The Earliest Triassic Yinkeng Formation is exposed at the well-known Meishan Section, South China, which contains the Global Stratotype of Section and Point （GSSP） for the Permian- Triassic boundary （PTB）. It reco...The Earliest Triassic Yinkeng Formation is exposed at the well-known Meishan Section, South China, which contains the Global Stratotype of Section and Point （GSSP） for the Permian- Triassic boundary （PTB）. It records centimeter-scale rhythmic alternations comprised mainly by marl- stone and limestone. Seven types of couplet embedded in five types of bundles were recognized based on occurrence and thickness of the lithologic units, suggesting that their formation was controlled by cyclic processes. The various orders of cycles observed correlate well with other Early Triassic counterparts recorded in South China. Here, we present new cyclostratigraphic results based on lithologic thickness and relative carbonate content of the Yinkeng Formation. Power spectra of carbonate content show that the ratio of major wavelengths recognized throughout the formation is similar to that of the 100 kyr short eccentricity, 33 kyr obliquity, and 21 kyr precession cycles, indicating that astronomical sig- nals are recorded in the Earliest Triassic rhythmic succession. Consistence between pronounced lithologic rhythmicity and sea-level changes obtained from Fischer plots indicates that high-frequency climatic cycles may have driven sea-level changes immediately after the PTB mass extinction. Fur- thermore, the 4th-order sea-level changes interpreted from the sedimentary record match well with 100 kyr short eccentricity component of carbonate content, reflecting that the 100 kyr short eccentricity- induced climate changes may have likely controlled the deposition of 4th-order sequences recognized from rhythmic successions.展开更多
Based on a large number of field outcrops and cores taken systematically from boreholes,by microscopic observa-tion,physical property analysis,mineralogy analysis,geochemical analysis etc.,reservoir characteristics of...Based on a large number of field outcrops and cores taken systematically from boreholes,by microscopic observa-tion,physical property analysis,mineralogy analysis,geochemical analysis etc.,reservoir characteristics of the first member of Middle Permian Maokou Formation in Sichuan Basin("Mao 1 Me mber"for short)are analyzed.(1)Rhythmic limestone-marl reservoirs of this member mostly exist in marl layers are a set of tight carbonate fracture-pore type reservoir with low porosity and low permeability,with multiple types of storage space,mainly secondary dissolution pores and fissures of clay minerals.(2)The clay minerals are mainly diagenetic clay minerals,such as sepiolite,talc and their intermediate products,aliettite,with hardly terrigenous clay minerals,and the reservoir in different regions have significant differences in the types of clay minerals.(3)The formation of high quality tight carbonate reservoir with limestone-marl interbeds is related to the differential diagene-sis in the early seawater burial stage and the exposure karstification in the early diagenetic stage.It is inferred through th e study that the inner ramp of southwestern Sichuan Basin is more likely to have sweet spots with high production,while the outer ramp in eastern Sichuan Basin is more likely to have large scale contiguous reservoir with low production.展开更多
基金supported by the National Program on Key Basic Research Project(No.2012CB822000)the Na-tional Natural Science Foundation of China(No.41302113)+3 种基金China Postdoctoral Science Foundation(No.2013M531765)the Foundation of State Key Laboratory of Petroleum Re-sources and Prospecting,China University of Petroleum,Bei-jing(No.PRP/open-1301)the Project of Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences(No.TPR-2012-06)the Fundamental Research Funds for the Central Universities of China(No.14CX02034A)
文摘The Earliest Triassic Yinkeng Formation is exposed at the well-known Meishan Section, South China, which contains the Global Stratotype of Section and Point （GSSP） for the Permian- Triassic boundary （PTB）. It records centimeter-scale rhythmic alternations comprised mainly by marl- stone and limestone. Seven types of couplet embedded in five types of bundles were recognized based on occurrence and thickness of the lithologic units, suggesting that their formation was controlled by cyclic processes. The various orders of cycles observed correlate well with other Early Triassic counterparts recorded in South China. Here, we present new cyclostratigraphic results based on lithologic thickness and relative carbonate content of the Yinkeng Formation. Power spectra of carbonate content show that the ratio of major wavelengths recognized throughout the formation is similar to that of the 100 kyr short eccentricity, 33 kyr obliquity, and 21 kyr precession cycles, indicating that astronomical sig- nals are recorded in the Earliest Triassic rhythmic succession. Consistence between pronounced lithologic rhythmicity and sea-level changes obtained from Fischer plots indicates that high-frequency climatic cycles may have driven sea-level changes immediately after the PTB mass extinction. Fur- thermore, the 4th-order sea-level changes interpreted from the sedimentary record match well with 100 kyr short eccentricity component of carbonate content, reflecting that the 100 kyr short eccentricity- induced climate changes may have likely controlled the deposition of 4th-order sequences recognized from rhythmic successions.
基金Supported by the Scientific and Technological Research Projects of Sinopec(P20059-3)Scientific and Technological Research Projects of Southwest Branch Company(KJ-633-2103).
文摘Based on a large number of field outcrops and cores taken systematically from boreholes,by microscopic observa-tion,physical property analysis,mineralogy analysis,geochemical analysis etc.,reservoir characteristics of the first member of Middle Permian Maokou Formation in Sichuan Basin("Mao 1 Me mber"for short)are analyzed.(1)Rhythmic limestone-marl reservoirs of this member mostly exist in marl layers are a set of tight carbonate fracture-pore type reservoir with low porosity and low permeability,with multiple types of storage space,mainly secondary dissolution pores and fissures of clay minerals.(2)The clay minerals are mainly diagenetic clay minerals,such as sepiolite,talc and their intermediate products,aliettite,with hardly terrigenous clay minerals,and the reservoir in different regions have significant differences in the types of clay minerals.(3)The formation of high quality tight carbonate reservoir with limestone-marl interbeds is related to the differential diagene-sis in the early seawater burial stage and the exposure karstification in the early diagenetic stage.It is inferred through th e study that the inner ramp of southwestern Sichuan Basin is more likely to have sweet spots with high production,while the outer ramp in eastern Sichuan Basin is more likely to have large scale contiguous reservoir with low production.
