In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the othe...In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the other three Tournaisian in age. These four depositional sequences appear to correlate fairly well with the four sequence recognized in Europe, North America and other areas. This may suggest that these sequences are synchronous depos- its resulted from the eustatic changes. The present study on sequence stratigraphy, biostratigraphy and event stratigraphy indicates that in neritic facies areas of South China, the Devonian-Carboniferous boundary, matching the boundary between Siphonodella praesulcata zone and S. sulcata zone in pelagic facies areas, is not only higher than the top of the Cystophrentis zone, but also higher than the top of the Devonian-Carboniferous boundary event bed. In neritic facies areas, the Devonian-Carbonifrerous boundary is marked by the most distinct transgressive surface within the Cystophrentiseudouralina interval zone, i. e. at the base of the TST of the SQ1. This boundary coincides with the top surface of the event bed resulted from the eustatic fall, and approximately corresponds to the basal part of Rseudouralina assemblage zone.展开更多
Detailed studies on Late Devonian to Early Carboniferous carbonate rocks in central Hunan, southern China have led to the recognition of 25 lithofacies which can be grouped into： （I） inner ramp peritidal platform, ...Detailed studies on Late Devonian to Early Carboniferous carbonate rocks in central Hunan, southern China have led to the recognition of 25 lithofacies which can be grouped into： （I） inner ramp peritidal platform, （2） inner ramp organic hank and mound, （3） mid ramp, （4） outer ramp, and （5） shelf basin facies associations. The peritidal platform facies association dominates the Zimenqiao Formation （Namurian A or late Datangian） and is characterized by gypsum and dolostone-containing sequences, indicating a peritidal platform environment. The other four facies associations dominate the Menggongao Formation （late Famennian）, Liujiatang Formation （Tournaisian or Yangruanian）, Shidengzi Formations （early Visean or early Datangian）. Five upward-shallowing cycles were distinguished in these three Formations. The predominant facies associations developed in each Formation demonstrate an overall transgression-regression cycle in the Late Devonian to Early Carboniferous in central Hunan. The overall transgressive sequence was preserved in the Shaodong, Menggongao, and Liujiatang Formations, and the overall regressive sequence was preserved in the Liujiatang, Shidengzi, Ceshui and Zimenqiao Formations.展开更多
Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore charact...Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs.A petrological nomenclature and classification scheme for bauxitic rocks based on three units(aluminum hydroxides,iron minerals and clay minerals)is proposed.It is found that bauxitic mudstone is in the form of dense massive and clastic structures,while the(clayey)bauxite is of dense massive,pisolite,oolite,porous soil and clastic structures.Both bauxitic mudstone and bauxite reservoirs develop dissolution pores,intercrystalline pores,and microfractures as the dominant gas storage space,with the porosity less than 10% and mesopores in dominance.The bauxite series in the North China Craton can be divided into five sections,i.e.,ferrilite(Shanxi-style iron ore,section A),bauxitic mudstone(section B),bauxite(section C),bauxite mudstone(debris-containing,section D)and dark mudstone-coal section(section E).The burrow/funnel filling,lenticular,layered/massive bauxite deposits occur separately in the karst platforms,gentle slopes and low-lying areas.The karst platforms and gentle slopes are conducive to surface water leaching,with strong karstification,well-developed pores,large reservoir thickness and good physical properties,but poor strata continuity.The low-lying areas have poor physical properties but relatively continuous and stable reservoirs.The gas enrichment in bauxites is jointly controlled by source rock,reservoir rock and fractures.This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.展开更多
The mudstone,gray tuffite and carbonaceous shale in the Upper Carboniferous Batamayineishan Formation(Bashan Formation)are essential source rocks for the volcanic reservoir in eastern Junggar,northwestern China.The ke...The mudstone,gray tuffite and carbonaceous shale in the Upper Carboniferous Batamayineishan Formation(Bashan Formation)are essential source rocks for the volcanic reservoir in eastern Junggar,northwestern China.The kerogen components,vitrinite reflectance,Rock-Eval pyrolysis,lipid biomarkers and isotope compositions were measured to understand the provenance and depositional environment of Bashan Formation under the background of volcanic activities.There were 10 and 4 periods of volcanic eruptions identified in the wells CS and DZ,respectively.The source rocks developed in the late or intermittent phase of volcanic activity.The original island arcs of the Early Carboniferous evolved into the Wucaiwan sag and the Dishuiquan sag in the Bashan Formation.The Wucaiwan sag inherited the restricted,closed residual sea,which had a slightly anoxic and hypersaline environment.The Dishuiquan sag was generally an oxidizing lacustrine environment,influenced by a marine transgression that may have occurred at the end of the DZ_(Ⅲ)period during the Late Carboniferous.Although the total organic matter decreased due to the volcanic eruption,ash could cause an increase of aquatic organisms,coinciding with increases in salinity and reducibility in the Dishuiquan sag.展开更多
山西平朔矿区上石炭统太原组11号煤层具有中硫、高灰、较高有机硫的特征,但其中各煤分层的基本性质差异较大,指示其成煤微环境显著变化。地球化学研究表明,Ca/ (Ca +Fe)、Th/U、Al/Ti、V/Zn、δEu、δCe可作为指示11号煤层沉积水介质盐...山西平朔矿区上石炭统太原组11号煤层具有中硫、高灰、较高有机硫的特征,但其中各煤分层的基本性质差异较大,指示其成煤微环境显著变化。地球化学研究表明,Ca/ (Ca +Fe)、Th/U、Al/Ti、V/Zn、δEu、δCe可作为指示11号煤层沉积水介质盐度的标志,St,d、So ,d/Sp,d可分别作为指示水介质氧化还原程度和酸碱度的标志,Ad、V/I、ΣREE可作为指示水介质动力条件的标志。在此基础上,分析了该煤层成煤微环境特征及其演化历程,认为11号煤层形成于波动式海进的半咸水—咸水沉积环境。在此过程中,海水对泥炭沼泽的影响经历了3个发展阶段:第1阶段,泥炭形成于微咸—半咸水条件,水动力条件逐渐增强;第2阶段,泥炭形成于半咸水—咸水条件,水动力条件总体上相对较强,沼泽水体从逐渐加深演化为显著变浅;第3阶段,泥炭形成于半咸水环境,海水影响再次逐渐增强,在泥炭沼泽演化末期水体显著变深,动力条件明显减弱,还原性显著增强。展开更多
文摘In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the other three Tournaisian in age. These four depositional sequences appear to correlate fairly well with the four sequence recognized in Europe, North America and other areas. This may suggest that these sequences are synchronous depos- its resulted from the eustatic changes. The present study on sequence stratigraphy, biostratigraphy and event stratigraphy indicates that in neritic facies areas of South China, the Devonian-Carboniferous boundary, matching the boundary between Siphonodella praesulcata zone and S. sulcata zone in pelagic facies areas, is not only higher than the top of the Cystophrentis zone, but also higher than the top of the Devonian-Carboniferous boundary event bed. In neritic facies areas, the Devonian-Carbonifrerous boundary is marked by the most distinct transgressive surface within the Cystophrentiseudouralina interval zone, i. e. at the base of the TST of the SQ1. This boundary coincides with the top surface of the event bed resulted from the eustatic fall, and approximately corresponds to the basal part of Rseudouralina assemblage zone.
基金supported by the National Natural Science Foundation of China(No.41030213)the Major National S&T Program of China(2011ZX05009-002)
文摘Detailed studies on Late Devonian to Early Carboniferous carbonate rocks in central Hunan, southern China have led to the recognition of 25 lithofacies which can be grouped into： （I） inner ramp peritidal platform, （2） inner ramp organic hank and mound, （3） mid ramp, （4） outer ramp, and （5） shelf basin facies associations. The peritidal platform facies association dominates the Zimenqiao Formation （Namurian A or late Datangian） and is characterized by gypsum and dolostone-containing sequences, indicating a peritidal platform environment. The other four facies associations dominate the Menggongao Formation （late Famennian）, Liujiatang Formation （Tournaisian or Yangruanian）, Shidengzi Formations （early Visean or early Datangian）. Five upward-shallowing cycles were distinguished in these three Formations. The predominant facies associations developed in each Formation demonstrate an overall transgression-regression cycle in the Late Devonian to Early Carboniferous in central Hunan. The overall transgressive sequence was preserved in the Shaodong, Menggongao, and Liujiatang Formations, and the overall regressive sequence was preserved in the Liujiatang, Shidengzi, Ceshui and Zimenqiao Formations.
基金Supported by the PetroChina Science and Technology Innovation Fund Project(2021DQ02-1003)Basic Research Project for Central Universities(2022JCCXDC02).
文摘Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs.A petrological nomenclature and classification scheme for bauxitic rocks based on three units(aluminum hydroxides,iron minerals and clay minerals)is proposed.It is found that bauxitic mudstone is in the form of dense massive and clastic structures,while the(clayey)bauxite is of dense massive,pisolite,oolite,porous soil and clastic structures.Both bauxitic mudstone and bauxite reservoirs develop dissolution pores,intercrystalline pores,and microfractures as the dominant gas storage space,with the porosity less than 10% and mesopores in dominance.The bauxite series in the North China Craton can be divided into five sections,i.e.,ferrilite(Shanxi-style iron ore,section A),bauxitic mudstone(section B),bauxite(section C),bauxite mudstone(debris-containing,section D)and dark mudstone-coal section(section E).The burrow/funnel filling,lenticular,layered/massive bauxite deposits occur separately in the karst platforms,gentle slopes and low-lying areas.The karst platforms and gentle slopes are conducive to surface water leaching,with strong karstification,well-developed pores,large reservoir thickness and good physical properties,but poor strata continuity.The low-lying areas have poor physical properties but relatively continuous and stable reservoirs.The gas enrichment in bauxites is jointly controlled by source rock,reservoir rock and fractures.This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.
基金financially supported by the National Natural Science Foundation of China(Nos.41503048,41872145)the Key Laboratory Project of Gansu Province(No.1309RTSA041)。
文摘The mudstone,gray tuffite and carbonaceous shale in the Upper Carboniferous Batamayineishan Formation(Bashan Formation)are essential source rocks for the volcanic reservoir in eastern Junggar,northwestern China.The kerogen components,vitrinite reflectance,Rock-Eval pyrolysis,lipid biomarkers and isotope compositions were measured to understand the provenance and depositional environment of Bashan Formation under the background of volcanic activities.There were 10 and 4 periods of volcanic eruptions identified in the wells CS and DZ,respectively.The source rocks developed in the late or intermittent phase of volcanic activity.The original island arcs of the Early Carboniferous evolved into the Wucaiwan sag and the Dishuiquan sag in the Bashan Formation.The Wucaiwan sag inherited the restricted,closed residual sea,which had a slightly anoxic and hypersaline environment.The Dishuiquan sag was generally an oxidizing lacustrine environment,influenced by a marine transgression that may have occurred at the end of the DZ_(Ⅲ)period during the Late Carboniferous.Although the total organic matter decreased due to the volcanic eruption,ash could cause an increase of aquatic organisms,coinciding with increases in salinity and reducibility in the Dishuiquan sag.
文摘山西平朔矿区上石炭统太原组11号煤层具有中硫、高灰、较高有机硫的特征,但其中各煤分层的基本性质差异较大,指示其成煤微环境显著变化。地球化学研究表明,Ca/ (Ca +Fe)、Th/U、Al/Ti、V/Zn、δEu、δCe可作为指示11号煤层沉积水介质盐度的标志,St,d、So ,d/Sp,d可分别作为指示水介质氧化还原程度和酸碱度的标志,Ad、V/I、ΣREE可作为指示水介质动力条件的标志。在此基础上,分析了该煤层成煤微环境特征及其演化历程,认为11号煤层形成于波动式海进的半咸水—咸水沉积环境。在此过程中,海水对泥炭沼泽的影响经历了3个发展阶段:第1阶段,泥炭形成于微咸—半咸水条件,水动力条件逐渐增强;第2阶段,泥炭形成于半咸水—咸水条件,水动力条件总体上相对较强,沼泽水体从逐渐加深演化为显著变浅;第3阶段,泥炭形成于半咸水环境,海水影响再次逐渐增强,在泥炭沼泽演化末期水体显著变深,动力条件明显减弱,还原性显著增强。
