2010 Vol. 35, No. 1
Display Method:
2010, 35(1): 1-10.
doi: 10.3799/dqkx.2010.001
PDF 885KB
Abstract:
Living planktonic foraminifers have been quantitatively analyzed on 40 plankton tow samples which were collected from 19 sites in the northern South China Sea (SCS) in September, 2004. The affecting factors on the distribution and compositions of foraminiferal faunal are then discussed. The results indicate that most foraminifera occurred in the autumn northern SCS are tropical warm water species, which apparently shows a regional distribution. The abundance of living foraminifera forms a general pattern with high abundance occurring in the northwest and relatively low values in the southeast of the studied area. The relative abundances of shallow water species G. sacculifer and G. ruber show high values near the coast area, and N. dutertrei are mainly distributed on the outer shelf and slope, and the high percentage of G. menardii mainly appeared at the southeast deep water area. G. calida and G. aequilateralis show similar distribution pattern, with high percentage at the deep water sites. Both of them show especial high values at the southernmost site off Vietnam. Our study suggests that the regional distribution of living planktonic foraminifers in the autumn northern SCS is mainly controlled by the combined impacts of primary productivity and water depth. High abundance usually appeared under high primary productivity area, and water depth also plays an important role on the distribution of subsurface dwelling species. The thickness, temperature and salinity of the mixed layer have no significant relationship with the distribution of living foraminifers in the autumn northern SCS, but the temperature and salinity structure of the lysocline do show significant relationship with the distribution of some subsurface dwelling species such as N. dutertrei、G. glutinata、G. calida and G. aequilateralis, In addition, the abundance of foraminifera is apparently higher in the warm eddies, with particularly higher percentage of G. sacculifer, than its adjacent sites, which suggests that warm eddy also has a significant influence on the distribution of planktonic foraminifera. P. obliquiloculata is only abundant in the northeastern part of the studied area which is affected by the branches of Kuroshio.
Living planktonic foraminifers have been quantitatively analyzed on 40 plankton tow samples which were collected from 19 sites in the northern South China Sea (SCS) in September, 2004. The affecting factors on the distribution and compositions of foraminiferal faunal are then discussed. The results indicate that most foraminifera occurred in the autumn northern SCS are tropical warm water species, which apparently shows a regional distribution. The abundance of living foraminifera forms a general pattern with high abundance occurring in the northwest and relatively low values in the southeast of the studied area. The relative abundances of shallow water species G. sacculifer and G. ruber show high values near the coast area, and N. dutertrei are mainly distributed on the outer shelf and slope, and the high percentage of G. menardii mainly appeared at the southeast deep water area. G. calida and G. aequilateralis show similar distribution pattern, with high percentage at the deep water sites. Both of them show especial high values at the southernmost site off Vietnam. Our study suggests that the regional distribution of living planktonic foraminifers in the autumn northern SCS is mainly controlled by the combined impacts of primary productivity and water depth. High abundance usually appeared under high primary productivity area, and water depth also plays an important role on the distribution of subsurface dwelling species. The thickness, temperature and salinity of the mixed layer have no significant relationship with the distribution of living foraminifers in the autumn northern SCS, but the temperature and salinity structure of the lysocline do show significant relationship with the distribution of some subsurface dwelling species such as N. dutertrei、G. glutinata、G. calida and G. aequilateralis, In addition, the abundance of foraminifera is apparently higher in the warm eddies, with particularly higher percentage of G. sacculifer, than its adjacent sites, which suggests that warm eddy also has a significant influence on the distribution of planktonic foraminifera. P. obliquiloculata is only abundant in the northeastern part of the studied area which is affected by the branches of Kuroshio.
2010, 35(1): 11-21.
doi: 10.3799/dqkx.2010.002
Abstract:
The studied area is situated at the origin of the Yangtze River in the Tanggula Mountain of southern Qinghai, which was a part of the Qamdo Block of the East Tethyan tectonic domain during the Late Palaeozoic and is bounded by the Jinshajiang suture to the north and the Lantsang-Lungmo Co suture to the south. The Permian strata is widespread in the area with various sedimentary facies, and separated by numerous and complicated faults, especially Lower Permian influenced by volcanic activity. As a result of complex regional tectonics and depositional types, there has been much controversy over the Lower Permian (Cisuralian) classification and correlation, which mainly involves issues including succession, age and regional correlation of volcanic rocks. According to the study of lithographic association of sedimentary environment and fauna of lithostratigraphical unit (especially volcanic rocks), the sequences in volcanic-sedimentary setting are refined in this paper. The Jiushidaoban and Nuoribagaribao formations are diachronous in southern Qinghai according to the fusulinid data. The Permian succession indicates that the Zharigen Formation composed mostly of carbonate rocks occupied the main part of the southern Qinghai, belonging to a stable platform during early stage of the Early Permian. The Luodianian strong volcanic eruption led to a depositional differentiation, forming the Qadikao Formation and contemporaneous Nuoribaribao Formation. As a result of volcanic product and sedimentary process, a complex volcanic-sedimentary landform occurred on sea floor and controlled the distribution of sedimentary facies. Four sedimentary types were recognized based on detailed field mapping and analysis of lithographic association. Jiushidaoban Formation mainly characterized by carbonate rock is widespread in southern Qinghai, which is a representative of platform facies during the intermission period between volcanic activities, which shows that the complex palaeogeographic structure of alternate volcano island and shallow marine has been transferred into a uniform and stable shallow-water carbonate platform since Xiangboan.
The studied area is situated at the origin of the Yangtze River in the Tanggula Mountain of southern Qinghai, which was a part of the Qamdo Block of the East Tethyan tectonic domain during the Late Palaeozoic and is bounded by the Jinshajiang suture to the north and the Lantsang-Lungmo Co suture to the south. The Permian strata is widespread in the area with various sedimentary facies, and separated by numerous and complicated faults, especially Lower Permian influenced by volcanic activity. As a result of complex regional tectonics and depositional types, there has been much controversy over the Lower Permian (Cisuralian) classification and correlation, which mainly involves issues including succession, age and regional correlation of volcanic rocks. According to the study of lithographic association of sedimentary environment and fauna of lithostratigraphical unit (especially volcanic rocks), the sequences in volcanic-sedimentary setting are refined in this paper. The Jiushidaoban and Nuoribagaribao formations are diachronous in southern Qinghai according to the fusulinid data. The Permian succession indicates that the Zharigen Formation composed mostly of carbonate rocks occupied the main part of the southern Qinghai, belonging to a stable platform during early stage of the Early Permian. The Luodianian strong volcanic eruption led to a depositional differentiation, forming the Qadikao Formation and contemporaneous Nuoribaribao Formation. As a result of volcanic product and sedimentary process, a complex volcanic-sedimentary landform occurred on sea floor and controlled the distribution of sedimentary facies. Four sedimentary types were recognized based on detailed field mapping and analysis of lithographic association. Jiushidaoban Formation mainly characterized by carbonate rock is widespread in southern Qinghai, which is a representative of platform facies during the intermission period between volcanic activities, which shows that the complex palaeogeographic structure of alternate volcano island and shallow marine has been transferred into a uniform and stable shallow-water carbonate platform since Xiangboan.
2010, 35(1): 22-30.
doi: 10.3799/dqkx.2010.003
Abstract:
In order to understand the relation between surface productivity changes and the evolution of the East Asian summer monsoon during the Quaternary glacial cycles in southern South China Sea, high-resolution study on content and accumulation rate of calcium carbonate and organic carbon of Core MD05-2897 were done to draw the conclusions as follows: the content and accumulation rate of calcium carbonate showed significant glacial-interglacial cycle change while organic carbon mainly showed a higher frequency of the periodic changes. Both of the content and the accumulation rate of calcium carbonate and organic carbon increased in the interglacial periods and decreased in the glacial periods, which reflects the enhancement of the summer monsoon in the interglacial periods caused the strengthening of the upwelling currents and the increase of nutrients, the surface productivity increased consequently. The most abundant spectrum periods of 100ka eccentricity, 40ka obliquity, 20ka precession and 10ka semi-precession indicate the characteristics of the low latitude sea areas responding to the orbital periods. The accumulation rate of calcium carbonate and organic carbon were in good agreement with summer insolation of low latitude in the Northern Hemisphere related to precession which may be the main controlling factor of East Asia summer monsoon changes, and climate changes related to the global ice volume is possibly the secondary controlling factor.
In order to understand the relation between surface productivity changes and the evolution of the East Asian summer monsoon during the Quaternary glacial cycles in southern South China Sea, high-resolution study on content and accumulation rate of calcium carbonate and organic carbon of Core MD05-2897 were done to draw the conclusions as follows: the content and accumulation rate of calcium carbonate showed significant glacial-interglacial cycle change while organic carbon mainly showed a higher frequency of the periodic changes. Both of the content and the accumulation rate of calcium carbonate and organic carbon increased in the interglacial periods and decreased in the glacial periods, which reflects the enhancement of the summer monsoon in the interglacial periods caused the strengthening of the upwelling currents and the increase of nutrients, the surface productivity increased consequently. The most abundant spectrum periods of 100ka eccentricity, 40ka obliquity, 20ka precession and 10ka semi-precession indicate the characteristics of the low latitude sea areas responding to the orbital periods. The accumulation rate of calcium carbonate and organic carbon were in good agreement with summer insolation of low latitude in the Northern Hemisphere related to precession which may be the main controlling factor of East Asia summer monsoon changes, and climate changes related to the global ice volume is possibly the secondary controlling factor.
2010, 35(1): 31-42.
doi: 10.3799/dqkx.2010.004
Abstract:
The major factors that govern the vertical distributions of redox sensitive elements (Fe, Mn, U and Mo) in interstitial water are studied by analyzing the measurement of concentrations of Fe, Mn, U and Mo in pore water and sediments in Yangtze estuary, combining with the early diagenesis model and geochemical thermodynamic analysis, The benthic fluxes of Fe, Mn, U and Mo have been calculated according to the Fick's first law. The results show that the concentrations of Fe, Mn, U and Mo in interstitial water in Yangtze Estuary sediments range from 0.8 to 106μmol/L, 14.8 to 258μmol/L, 1.9 to 14.4nmol/L and 60 to 546nmol/L, respectively. The maximum of interstitial Fe2+ and Mn2+ have been observed at 5cm or 10cm in the vertical profiles, respectively. The interstitial iron and manganese profiles are mainly controlled by early diagenetic processes in Yangtze Estuary sediments. Adsorption process has great effect on the distribution of interstitial Fe2+ and Mn2+. The greater the adsorption coefficients are, the less the concentrations of interstitial Fe2+ and Mn2+ are. The vertical distributions of interstitial uranium are mainly controlled by iron. However, there is no correlation between Mo and Fe or Mn. The calculated diffusive fluxes of Fe, Mn, U and Mo range from 3 to 10.5μmol·(m2·d)-1, 35.7 to 439.5μmol·(m2·d)-1, -2.3 to 0.2nmol·(m2·d)-1 and -36 to 94.6nmol·(m2·d)-1, respectively. The ratio of authigenic uranium to total uranium ranges from 6% to 67%.
The major factors that govern the vertical distributions of redox sensitive elements (Fe, Mn, U and Mo) in interstitial water are studied by analyzing the measurement of concentrations of Fe, Mn, U and Mo in pore water and sediments in Yangtze estuary, combining with the early diagenesis model and geochemical thermodynamic analysis, The benthic fluxes of Fe, Mn, U and Mo have been calculated according to the Fick's first law. The results show that the concentrations of Fe, Mn, U and Mo in interstitial water in Yangtze Estuary sediments range from 0.8 to 106μmol/L, 14.8 to 258μmol/L, 1.9 to 14.4nmol/L and 60 to 546nmol/L, respectively. The maximum of interstitial Fe2+ and Mn2+ have been observed at 5cm or 10cm in the vertical profiles, respectively. The interstitial iron and manganese profiles are mainly controlled by early diagenetic processes in Yangtze Estuary sediments. Adsorption process has great effect on the distribution of interstitial Fe2+ and Mn2+. The greater the adsorption coefficients are, the less the concentrations of interstitial Fe2+ and Mn2+ are. The vertical distributions of interstitial uranium are mainly controlled by iron. However, there is no correlation between Mo and Fe or Mn. The calculated diffusive fluxes of Fe, Mn, U and Mo range from 3 to 10.5μmol·(m2·d)-1, 35.7 to 439.5μmol·(m2·d)-1, -2.3 to 0.2nmol·(m2·d)-1 and -36 to 94.6nmol·(m2·d)-1, respectively. The ratio of authigenic uranium to total uranium ranges from 6% to 67%.
2010, 35(1): 43-50.
doi: 10.3799/dqkx.2010.005
Abstract:
Based on the the hydrological and meteorological data in Lijiang basin, the precipitation, groundwater and runoff in this typical monsoonal temperate glacier area increase significantly, which suggests that water cycle over the region more rapidly under the climate warming. The increase amplitude of runoff in the downstream region of the glaciated area is much stronger than that of precipitation, resulting from the prominent increase of melt water from Mt. Yulong. It indicates that the contribution made by melt water to runoff increase is great under the climate warming, especially in autumn, winter and spring. It is also obvious in Hailuogou basin according to the preliminary analysis of the observational hydrological and meteorological data. The results in this paper are significant to study the glacier variation, water balance and glacier disaster in Chinese monsoonal temperate glacier regions.
Based on the the hydrological and meteorological data in Lijiang basin, the precipitation, groundwater and runoff in this typical monsoonal temperate glacier area increase significantly, which suggests that water cycle over the region more rapidly under the climate warming. The increase amplitude of runoff in the downstream region of the glaciated area is much stronger than that of precipitation, resulting from the prominent increase of melt water from Mt. Yulong. It indicates that the contribution made by melt water to runoff increase is great under the climate warming, especially in autumn, winter and spring. It is also obvious in Hailuogou basin according to the preliminary analysis of the observational hydrological and meteorological data. The results in this paper are significant to study the glacier variation, water balance and glacier disaster in Chinese monsoonal temperate glacier regions.
2010, 35(1): 51-61.
doi: 10.3799/dqkx.2010.006
Abstract:
The Lower-Middle Triassic strata in Qingyan, Guizhou are well exposed and have abundant fossils. In particular, the Qingyan fauna in Middle Triassic shows biota radiation. The stratigraphical sequence has been studied extensively for a better understanding of the course and pattern of the biotic recovery and radiation following the End-Permian mass extinction. Five conodont zones, including Neospathodus dieneri zone, Neospathodus waageni zone, Neospathodus pingdingshanensis zone, Neospathodus homeri zone, and Chiosella timorensis zone, 2 foraminifer assemblages and 6 bivalve assemblages are recognized. The boudaries of Induan-Olenekian and Olenekian-Anisian have been defined by the conodonts. Various fossils and their ecologic assemblages indicate that the first episode of recovery-radiation after the End-Permian extinction happened in the early Ainisian, and the fossil assemblages in Leidapo Member (Middle Anisian) reveal a typical prosperous biotic ecosystem after radiation. The brachiopod assemblages, Madoia sp. assemblage and Rhaetina angustaeformis assemblage, from the Middle Anisian Qingyan Formation represent the first radiation of brachiopod faunas from the recovery. In addition, the sedimentary evidence indicates two up-shallowing cycles of paleoenvironmental setting, basin-slope-platform-basin-slope-shelf.
The Lower-Middle Triassic strata in Qingyan, Guizhou are well exposed and have abundant fossils. In particular, the Qingyan fauna in Middle Triassic shows biota radiation. The stratigraphical sequence has been studied extensively for a better understanding of the course and pattern of the biotic recovery and radiation following the End-Permian mass extinction. Five conodont zones, including Neospathodus dieneri zone, Neospathodus waageni zone, Neospathodus pingdingshanensis zone, Neospathodus homeri zone, and Chiosella timorensis zone, 2 foraminifer assemblages and 6 bivalve assemblages are recognized. The boudaries of Induan-Olenekian and Olenekian-Anisian have been defined by the conodonts. Various fossils and their ecologic assemblages indicate that the first episode of recovery-radiation after the End-Permian extinction happened in the early Ainisian, and the fossil assemblages in Leidapo Member (Middle Anisian) reveal a typical prosperous biotic ecosystem after radiation. The brachiopod assemblages, Madoia sp. assemblage and Rhaetina angustaeformis assemblage, from the Middle Anisian Qingyan Formation represent the first radiation of brachiopod faunas from the recovery. In addition, the sedimentary evidence indicates two up-shallowing cycles of paleoenvironmental setting, basin-slope-platform-basin-slope-shelf.
2010, 35(1): 65-74.
doi: 10.3799/dqkx.2010.007
Abstract:
Loess origin of Zoigê basin has been discussed based on synthetic study in grain compositions of the loess, surface texture of quartz sand, as well as other geological phenomena. On the probability cumulative curve of loess, saltation mass and suspension are obvious, and the latter is dominant. Matrix method is adopted to compute grain size of the loess. The statistic analysis on quartz sand surface textures of loess through scanning electron microscope shows the features of air transportation, developed dishing pit, and combined profile features of Aeolian environment. In addition, sporo-pollens are scarce in the loess and ice-wedges are discovered in the neighboring loess strata. The above analysis shows that Zoigê basin loess is Aeolian sediment in the periglacial environment, the age of loess formation mainly are Chazhenliangzi loess of Malan period and Suokezang Temple loess of Lishi period.
Loess origin of Zoigê basin has been discussed based on synthetic study in grain compositions of the loess, surface texture of quartz sand, as well as other geological phenomena. On the probability cumulative curve of loess, saltation mass and suspension are obvious, and the latter is dominant. Matrix method is adopted to compute grain size of the loess. The statistic analysis on quartz sand surface textures of loess through scanning electron microscope shows the features of air transportation, developed dishing pit, and combined profile features of Aeolian environment. In addition, sporo-pollens are scarce in the loess and ice-wedges are discovered in the neighboring loess strata. The above analysis shows that Zoigê basin loess is Aeolian sediment in the periglacial environment, the age of loess formation mainly are Chazhenliangzi loess of Malan period and Suokezang Temple loess of Lishi period.
2010, 35(1): 75-86.
doi: 10.3799/dqkx.2010.008
Abstract:
It has geological and mode of occurrence differences between mud diapirs and mud volcanoes though the similar genesis and the characters of evolution and development. Mud diapirs in Yinggehai basin located in the central deep depression, appeared on five north-west lines and had characters of low density, low wave velocity, high temperature and high pressure however mud volcanoes in Southwest Taiwan basin located in the continental deep-water distract in the south depression and Tainan-Kaohsiung distract in Taiwan. It located along the discordogenic fault and usually had calderas also sea floors. Mud diapirs and mud volcanoes had many styles of accompanying gas to be mainly of the mature-post mature coaliferous gas and had abundence CO2 and N2 to be mainly of the inorganic-crustal CO2. The mud formations were Miocene and Pliocene marine mud shales which was souce rocks, furthermore it made a effictive system with the channel and affiliated structures generated by mud diapirs and mud volcanoes, so it was a particular petroleum system controlling the distribution of oil and gas.
It has geological and mode of occurrence differences between mud diapirs and mud volcanoes though the similar genesis and the characters of evolution and development. Mud diapirs in Yinggehai basin located in the central deep depression, appeared on five north-west lines and had characters of low density, low wave velocity, high temperature and high pressure however mud volcanoes in Southwest Taiwan basin located in the continental deep-water distract in the south depression and Tainan-Kaohsiung distract in Taiwan. It located along the discordogenic fault and usually had calderas also sea floors. Mud diapirs and mud volcanoes had many styles of accompanying gas to be mainly of the mature-post mature coaliferous gas and had abundence CO2 and N2 to be mainly of the inorganic-crustal CO2. The mud formations were Miocene and Pliocene marine mud shales which was souce rocks, furthermore it made a effictive system with the channel and affiliated structures generated by mud diapirs and mud volcanoes, so it was a particular petroleum system controlling the distribution of oil and gas.
2010, 35(1): 87-96.
doi: 10.3799/dqkx.2010.009
Abstract:
Based on the core description, microanalysis and processing of the logging data including AC, GR and DEN, a new type of silicalite reservoirs in Paleozoic buried hill in Zhuanghai area is found whose rock-electric properties are very different from those of protogenesis silicalites. Silicalite reservoirs are called silicified rock here and their characteristics are generalized. The structure of primary rock of silicified rock is clear and the idiomorphic degree of quartz crystal is high. Paragentic hydrothermal mineral assemblage of fluorite, barite, pyrite, ferrocalcite and quartz with secondary characteristic are common in silicified rock layer and the secondary corrosion of these paragentic hydrothermal minerals is significant. The pore of silicified layer is very developed including not only large solution cavities among breccias and secondary pores by dissolution of the Paragentic hydrothermal minerals, but also the micro-pores among the idiomorphic quartz crystal druse. The P-wave velocity and the density of silicified rock are much lower than that of the carbonate and the distribution of silicified rock in buried hill is featured with the "cross-layer" characteristic. By comparing with the characteristic of the protogenesis silicalite in Paleozoic buried hill, it is believed that the silicified rock is secondary genesis which resulted from deep buried modification. The secondary silicified rock is a new type of reservoir of Paleozoic buried hill in Zhuanghai area. The discovery of this new kind of reservoirs is not only of value to the high exploration basin, but also of scientific significance to the advance of silicate research.
Based on the core description, microanalysis and processing of the logging data including AC, GR and DEN, a new type of silicalite reservoirs in Paleozoic buried hill in Zhuanghai area is found whose rock-electric properties are very different from those of protogenesis silicalites. Silicalite reservoirs are called silicified rock here and their characteristics are generalized. The structure of primary rock of silicified rock is clear and the idiomorphic degree of quartz crystal is high. Paragentic hydrothermal mineral assemblage of fluorite, barite, pyrite, ferrocalcite and quartz with secondary characteristic are common in silicified rock layer and the secondary corrosion of these paragentic hydrothermal minerals is significant. The pore of silicified layer is very developed including not only large solution cavities among breccias and secondary pores by dissolution of the Paragentic hydrothermal minerals, but also the micro-pores among the idiomorphic quartz crystal druse. The P-wave velocity and the density of silicified rock are much lower than that of the carbonate and the distribution of silicified rock in buried hill is featured with the "cross-layer" characteristic. By comparing with the characteristic of the protogenesis silicalite in Paleozoic buried hill, it is believed that the silicified rock is secondary genesis which resulted from deep buried modification. The secondary silicified rock is a new type of reservoir of Paleozoic buried hill in Zhuanghai area. The discovery of this new kind of reservoirs is not only of value to the high exploration basin, but also of scientific significance to the advance of silicate research.
2010, 35(1): 97-106.
doi: 10.3799/dqkx.2010.010
Abstract:
Based on analyzing the previous problems relative to sequence stratigraphy researches on Erlian basin, this paper associated with the theories and methods of tecto-stratigraphy, genetic stratigraphy and sequence stratigraphy.We take the boundaries of basin generation and boundaries of basin prototype with regional correlative significations as first-order and second-orders in the scenario of framework sequence stratigraphy. And every cycle (para-type basin) representing rift and tectonic inversion within basin (or depression) type is divided as third-order sequences, and the subsidence-filling unit as fourth-order sequences. This paper is to analyze sequence stratigraphic framework based on the restriction of tectonic-sedimentation, and to analyze genetic stratigraphic framework under sequence stratigraphic framework. The merits in the scenario of framework sequence stratigraphy are that it inherits the analysis of chronostratigraphic boundary, sequence cycle and accommodation within marine sequence stratigraphy, and abandon part component of sea-level change and systems tracts in marine setting that are unsuitable in continental rift basin. Such scenario is convenient to construct the unifying sequence stratigraphic framework abroad entire basin, and to express sedimentary characteristics and developments of every sequence stratigraphic unit as well as hydrocarbon pool forming conditions located on different structure-lithofacies zones. In the meantime, this scenario will help to promote cognizing distributions and regional differences of favorable reservoirs and their facies belts so as to establish the significant model of hydrocarbon pool formation and accumulation. Based on practical analyses in all sags within Erlian basin, this paper has constructed correlative, obviously disciplinary and unifying boundary-ordered systems and correlative sequence stratigraphic framework.
Based on analyzing the previous problems relative to sequence stratigraphy researches on Erlian basin, this paper associated with the theories and methods of tecto-stratigraphy, genetic stratigraphy and sequence stratigraphy.We take the boundaries of basin generation and boundaries of basin prototype with regional correlative significations as first-order and second-orders in the scenario of framework sequence stratigraphy. And every cycle (para-type basin) representing rift and tectonic inversion within basin (or depression) type is divided as third-order sequences, and the subsidence-filling unit as fourth-order sequences. This paper is to analyze sequence stratigraphic framework based on the restriction of tectonic-sedimentation, and to analyze genetic stratigraphic framework under sequence stratigraphic framework. The merits in the scenario of framework sequence stratigraphy are that it inherits the analysis of chronostratigraphic boundary, sequence cycle and accommodation within marine sequence stratigraphy, and abandon part component of sea-level change and systems tracts in marine setting that are unsuitable in continental rift basin. Such scenario is convenient to construct the unifying sequence stratigraphic framework abroad entire basin, and to express sedimentary characteristics and developments of every sequence stratigraphic unit as well as hydrocarbon pool forming conditions located on different structure-lithofacies zones. In the meantime, this scenario will help to promote cognizing distributions and regional differences of favorable reservoirs and their facies belts so as to establish the significant model of hydrocarbon pool formation and accumulation. Based on practical analyses in all sags within Erlian basin, this paper has constructed correlative, obviously disciplinary and unifying boundary-ordered systems and correlative sequence stratigraphic framework.
2010, 35(1): 107-114.
doi: 10.3799/dqkx.2010.011
Abstract:
The degree of laumontites development and the status of laumontites dissolution are important indexes for the prediction of potential sedimentary belt in extra-low permeability formations of Yanchang group in Ordos basin. Laumontite is not only distributed in the deep reservoir such as Chang 6 of the northeast Ordos basin, but also extensively distributed in the shallow reservoir such as Chang 3 of Fuxian exploration area in the southeast basin. The main reason is that the Chang 3 reservoir of Fuxian exploration area has a great quantity of plagioclase. In the later period of early diagenetic stage, laumontite and the alkaline pore water which was rich in Na were interactional, and the laumontite cement was formed. Through measuring inclusions in laumontite, we find out that its forming temperature is between 85-100℃. The development of laumontite was controlled by sedimentary micro-facies and the sequences stacked of sandbody, and it was mostly distributed in the delta plain and delta front stacked of the distributary channels compound sandbody. In the early period of later diagenetic stage, laumontite were dissolved by organic acid which was generated in decarboxylation of kerogen, and a great quantity of secondary pores were formed. The total effect of the laumontites sedimentation and dissolution led to the increased porosity in the Fuxian exploration east area and the reduced porosity in the west area. The development of laumontite dissoluted secondary pore was the main control factor of the high quality reservoirs in Yanchang Formation of Fuxian exploration area.
The degree of laumontites development and the status of laumontites dissolution are important indexes for the prediction of potential sedimentary belt in extra-low permeability formations of Yanchang group in Ordos basin. Laumontite is not only distributed in the deep reservoir such as Chang 6 of the northeast Ordos basin, but also extensively distributed in the shallow reservoir such as Chang 3 of Fuxian exploration area in the southeast basin. The main reason is that the Chang 3 reservoir of Fuxian exploration area has a great quantity of plagioclase. In the later period of early diagenetic stage, laumontite and the alkaline pore water which was rich in Na were interactional, and the laumontite cement was formed. Through measuring inclusions in laumontite, we find out that its forming temperature is between 85-100℃. The development of laumontite was controlled by sedimentary micro-facies and the sequences stacked of sandbody, and it was mostly distributed in the delta plain and delta front stacked of the distributary channels compound sandbody. In the early period of later diagenetic stage, laumontite were dissolved by organic acid which was generated in decarboxylation of kerogen, and a great quantity of secondary pores were formed. The total effect of the laumontites sedimentation and dissolution led to the increased porosity in the Fuxian exploration east area and the reduced porosity in the west area. The development of laumontite dissoluted secondary pore was the main control factor of the high quality reservoirs in Yanchang Formation of Fuxian exploration area.
2010, 35(1): 115-124.
doi: 10.3799/dqkx.2010.012
Abstract:
The mudstones of the Es3 formation in Banqiao depression are the dominant source rocks for the major hydrocarbon accumulations and the sandstones of Es3 formation are major reservoir rocks. Petroleum generation, migration and accumulation history of the Es3 formation in Banqiao depression are modelled based on reconstruction of the burial, thermal and maturity history in this paper. The Modelling results are calibrated with measured vitrinite reflectance (Ro), borehole temperatures and drilling results of 63 wells. The modelling results indicate that: (1) the present-day heat flow in Banqiao depression varies from 59.8 to 61.7mW/m2 and that the paleoheat flow increased from 65 to 50.4Ma, reaching peak heat flow values at 50.4Ma then decreased with from 50.4 to 0Ma; (2) the source rocks maturity of Es3 formation ranges from 0.75% to 1.8% Ro at present day and from 0.5% to 1.25% Ro at the end of the Ed formation deposition (26Ma). Oil generation (0.5% Ro) in Es3 formation began from around 35Ma and peak hydrocarbon generation (1.0% Ro) occured from 30Ma; (3) the timing of hydrocarbon expulsion from Es3 formation source rocks began from 31Ma, the predominant phase of hydrocarbon expulsion is from 31 to 26Ma and the phase of less hydrocarbon expulsion is from 26 to 0Ma; (4) secondary petroleum migration pathways of Es3 formation of Banqiao depression at present and 26Ma are controlled by the paleo-structure surface and the spreading flowing, confluence flowing and the planar flowing occur in depression zone, the gentle slope zone and the steep slope zone respectively. Six favorable zones of oil accumulations in the Es3 formation of Banqiao depression are identified, especially the oil accumulations zone Ⅰ and Ⅱ, due to their location being close to the generative kitchens, short oil migration distance and powerful drive force.
The mudstones of the Es3 formation in Banqiao depression are the dominant source rocks for the major hydrocarbon accumulations and the sandstones of Es3 formation are major reservoir rocks. Petroleum generation, migration and accumulation history of the Es3 formation in Banqiao depression are modelled based on reconstruction of the burial, thermal and maturity history in this paper. The Modelling results are calibrated with measured vitrinite reflectance (Ro), borehole temperatures and drilling results of 63 wells. The modelling results indicate that: (1) the present-day heat flow in Banqiao depression varies from 59.8 to 61.7mW/m2 and that the paleoheat flow increased from 65 to 50.4Ma, reaching peak heat flow values at 50.4Ma then decreased with from 50.4 to 0Ma; (2) the source rocks maturity of Es3 formation ranges from 0.75% to 1.8% Ro at present day and from 0.5% to 1.25% Ro at the end of the Ed formation deposition (26Ma). Oil generation (0.5% Ro) in Es3 formation began from around 35Ma and peak hydrocarbon generation (1.0% Ro) occured from 30Ma; (3) the timing of hydrocarbon expulsion from Es3 formation source rocks began from 31Ma, the predominant phase of hydrocarbon expulsion is from 31 to 26Ma and the phase of less hydrocarbon expulsion is from 26 to 0Ma; (4) secondary petroleum migration pathways of Es3 formation of Banqiao depression at present and 26Ma are controlled by the paleo-structure surface and the spreading flowing, confluence flowing and the planar flowing occur in depression zone, the gentle slope zone and the steep slope zone respectively. Six favorable zones of oil accumulations in the Es3 formation of Banqiao depression are identified, especially the oil accumulations zone Ⅰ and Ⅱ, due to their location being close to the generative kitchens, short oil migration distance and powerful drive force.
2010, 35(1): 125-136.
doi: 10.3799/dqkx.2010.013
Abstract:
Four phases of oolitic shoal developed in the inner parasequence set 1, parasequence set 2, parasequence set 3 and parasequence set 4 respectively in the forepart of Feixianguan Formation in Yudongzi section of Erlangmiao, Jiangyou. Parasequence set 1 is composed of parasequence 1 and parasequence 2. The later development at the edge of the stabilized sand flat around area with deep water is the main body of oolitic shoal. It is dominated by ooid-silty-fine limestone and oolitic limestone in which ooids are smaller with the diameter ranging from 0.3mm to 0.8mm, moderate-sorted and rounded-subrounded with the increasing of contents ascending from about 20% to 50%-60%. Parasequence set 2 is composed of parasequence 1, parasequence 2 and parasequence 3. The upside of parasequence 1, parasequence 2 and parasequence 3 are all the main body of oolitic shoal developed at the edge of the stabilized sand flat. They are dominated by pisolitic-oolitic limestone and oolitic-pisolitic limestone in which the contents of grains are 40%-65%. Ooids are bigger with the diameter varying from 0.2mm to 1.8mm, poorly-sorted and rounded-subrounded. Parasequence set 3 is composed of parasequence 1 and parasequence 2. Both of them are the main body of oolitic shoal and developed at the edge of the stabilized sand flat around area with the mobile fringe. They are dominated by oolitic limestone in which the contents of grains are 40%-70%. Ooids are a little smaller with the diameter ranging from 0.1mm to 0.8mm, moderate or poorly-sorted and subrounded. Parasequence set 4 is composed of parasequence 1, parasequence 2, parasequence 3, parasequence 4 and parasequence 5. The last four developed on the mobile fringe are the main body of oolitic shoal. Ooids at the bottom of each parasequence which are dominated by dolomitic-oolitic limestone are small with the diameter ranging from 0.2mm to 0.8mm, moderate or poorly-sorted and well-rounded with the contents of 50%-60%, while those on the top dominated by residual oolitic dolostones are much smaller with the diameter ranging from 0.2mm to 0.5mm, well-sorted and well-rounded with the contents of over 80%. By the analogs of oolitic shoal and testing of physical properties, it is found that high-quality reservoir is developed in the mobile fringe where the hydrodynamic conditions are stronger. The reservoir in which the contents of grains in the oolitic shoal are more than 55% and the contents of dolomite are more than 60% have better physical properties with porosities of 10.94% and permeabilities of 0.076×10-3μm2 on average. Thus it can be seen the mobile fringe is the position where potential high-quality reservoirs develop and the forming of them are highly related with their original sediment conditions.
Four phases of oolitic shoal developed in the inner parasequence set 1, parasequence set 2, parasequence set 3 and parasequence set 4 respectively in the forepart of Feixianguan Formation in Yudongzi section of Erlangmiao, Jiangyou. Parasequence set 1 is composed of parasequence 1 and parasequence 2. The later development at the edge of the stabilized sand flat around area with deep water is the main body of oolitic shoal. It is dominated by ooid-silty-fine limestone and oolitic limestone in which ooids are smaller with the diameter ranging from 0.3mm to 0.8mm, moderate-sorted and rounded-subrounded with the increasing of contents ascending from about 20% to 50%-60%. Parasequence set 2 is composed of parasequence 1, parasequence 2 and parasequence 3. The upside of parasequence 1, parasequence 2 and parasequence 3 are all the main body of oolitic shoal developed at the edge of the stabilized sand flat. They are dominated by pisolitic-oolitic limestone and oolitic-pisolitic limestone in which the contents of grains are 40%-65%. Ooids are bigger with the diameter varying from 0.2mm to 1.8mm, poorly-sorted and rounded-subrounded. Parasequence set 3 is composed of parasequence 1 and parasequence 2. Both of them are the main body of oolitic shoal and developed at the edge of the stabilized sand flat around area with the mobile fringe. They are dominated by oolitic limestone in which the contents of grains are 40%-70%. Ooids are a little smaller with the diameter ranging from 0.1mm to 0.8mm, moderate or poorly-sorted and subrounded. Parasequence set 4 is composed of parasequence 1, parasequence 2, parasequence 3, parasequence 4 and parasequence 5. The last four developed on the mobile fringe are the main body of oolitic shoal. Ooids at the bottom of each parasequence which are dominated by dolomitic-oolitic limestone are small with the diameter ranging from 0.2mm to 0.8mm, moderate or poorly-sorted and well-rounded with the contents of 50%-60%, while those on the top dominated by residual oolitic dolostones are much smaller with the diameter ranging from 0.2mm to 0.5mm, well-sorted and well-rounded with the contents of over 80%. By the analogs of oolitic shoal and testing of physical properties, it is found that high-quality reservoir is developed in the mobile fringe where the hydrodynamic conditions are stronger. The reservoir in which the contents of grains in the oolitic shoal are more than 55% and the contents of dolomite are more than 60% have better physical properties with porosities of 10.94% and permeabilities of 0.076×10-3μm2 on average. Thus it can be seen the mobile fringe is the position where potential high-quality reservoirs develop and the forming of them are highly related with their original sediment conditions.
2010, 35(1): 137-145.
doi: 10.3799/dqkx.2010.014
Abstract:
Lile basin is a hot research spot in Nansha area. We probe into the petroleum potential of Lile basin based on geological and geophysical analysis of seismic profiles, wells and dredging data. All necessary elements for a hydrocarbon accumulation are analyzed in the basin. We suggest that the Mesozoic to early Cenozoic sediments are the major source rock. Potential reservoirs include the late Oligocene reefs and Mesozoic aerated layer. The principal play-types recognized in the basin are the Late Oligocene to Early Miocene reefs and erosional Mesozoic faulted blocks. Long term active faults connect the Mesozoic source rock and shallow layer play, so the faults are major transport channel and control the spatial distribution of hydrocarbon reservoir. Similar to the Dongsha movement in the northern of South China Sea, Late Miocene tectonic event was good for hydrocarbon migration. The attenuated tectonic movement thereafter benefited the hydrocarbon accumulation.
Lile basin is a hot research spot in Nansha area. We probe into the petroleum potential of Lile basin based on geological and geophysical analysis of seismic profiles, wells and dredging data. All necessary elements for a hydrocarbon accumulation are analyzed in the basin. We suggest that the Mesozoic to early Cenozoic sediments are the major source rock. Potential reservoirs include the late Oligocene reefs and Mesozoic aerated layer. The principal play-types recognized in the basin are the Late Oligocene to Early Miocene reefs and erosional Mesozoic faulted blocks. Long term active faults connect the Mesozoic source rock and shallow layer play, so the faults are major transport channel and control the spatial distribution of hydrocarbon reservoir. Similar to the Dongsha movement in the northern of South China Sea, Late Miocene tectonic event was good for hydrocarbon migration. The attenuated tectonic movement thereafter benefited the hydrocarbon accumulation.
2010, 35(1): 146-154.
doi: 10.3799/dqkx.2010.015
Abstract:
The present work is designed to simulate the dissolution of sulphate rock under various conditions of different bacterial cell numbers, temperatures and reaction times both in water-rock and water-rock-bacteria systems by laboratory experiment. The results show that chemical dissolution of sulphate rock is dominated in water-rock system, while bacterial sulphate reduction process and the dissolution of sulphate rock driven by bacterial sulphate reduction are dominated in water-rock-bacteria system. The dissolution of sulphate rock driven by bacterial sulphate reduction resultes in the formation of sulphate karst, which enhances the permeability of carbonate rock coexisted with sulphate rock. The research is an insight into biokarst, which provides a new perspective for the field of petroleum geology.
The present work is designed to simulate the dissolution of sulphate rock under various conditions of different bacterial cell numbers, temperatures and reaction times both in water-rock and water-rock-bacteria systems by laboratory experiment. The results show that chemical dissolution of sulphate rock is dominated in water-rock system, while bacterial sulphate reduction process and the dissolution of sulphate rock driven by bacterial sulphate reduction are dominated in water-rock-bacteria system. The dissolution of sulphate rock driven by bacterial sulphate reduction resultes in the formation of sulphate karst, which enhances the permeability of carbonate rock coexisted with sulphate rock. The research is an insight into biokarst, which provides a new perspective for the field of petroleum geology.
2010, 35(1): 155-160.
doi: 10.3799/dqkx.2010.016
Abstract:
The South Jingyang plateau, which has a total area of 70km2, is located in Shaanxi Province, China. Groundwater table in this loess plateau has been significantly raised since 1976 when the loess cover began to be artificially irrigated. Up to now, more than 50 landslide events at 27 sites have occurred not only resulting in large economic loss and numerous deaths but also exacerbating water and soil erosion that reduced plateau area badly. After filed visits and landslide measurement at South Jingyang plateau, the following types of loess landslides there can be recognized on the basis of the initiative mechanisms: loess flowslide, loess slide and loess fall. We also analyzed the mechanisms of terrain-edge cracks and steep scarp and their relations with group-distribution and retrogressive occurrences of loess landslide. The mechanism of the long runout loess landslide has also been discussed.
The South Jingyang plateau, which has a total area of 70km2, is located in Shaanxi Province, China. Groundwater table in this loess plateau has been significantly raised since 1976 when the loess cover began to be artificially irrigated. Up to now, more than 50 landslide events at 27 sites have occurred not only resulting in large economic loss and numerous deaths but also exacerbating water and soil erosion that reduced plateau area badly. After filed visits and landslide measurement at South Jingyang plateau, the following types of loess landslides there can be recognized on the basis of the initiative mechanisms: loess flowslide, loess slide and loess fall. We also analyzed the mechanisms of terrain-edge cracks and steep scarp and their relations with group-distribution and retrogressive occurrences of loess landslide. The mechanism of the long runout loess landslide has also been discussed.
