Eocene Sedimentary–Diagenetic Environment Analysis of the Pingtai Area of the Qaidam Basin
Based on the petrological characteristics and elemental geochemical analysis of core samples from the Pingtai area in the northern structural belt of the Qaidam Basin, this study shows that the clay mineral assemblage of Lulehe Formation sandstone is dominated by high contents of smectite, chlorite...
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MDPI AG
2022-07-01
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| author | Guoqiang Sun Shuncun Zhang Yetong Wang Yaoliang Li Hui Guo Shangshang Bo |
| author_facet | Guoqiang Sun Shuncun Zhang Yetong Wang Yaoliang Li Hui Guo Shangshang Bo |
| author_sort | Guoqiang Sun |
| collection | DOAJ |
| description | Based on the petrological characteristics and elemental geochemical analysis of core samples from the Pingtai area in the northern structural belt of the Qaidam Basin, this study shows that the clay mineral assemblage of Lulehe Formation sandstone is dominated by high contents of smectite, chlorite and illite, and does not contain illite–smectite mixed layers or kaolinite. The chlorite and illite in the Xiaganchaigou Formation decreased gradually and the smectite disappeared. In addition, illite–smectite mixed layers began to appear and kaolinite was not present. These results indicate that the diagenetic environment of the Pingtai area in the early Eocene was dominated by alkaline media poor in K<sup>+</sup> and rich in Mg<sup>2+</sup>, Na<sup>+</sup> and Ca<sup>2+</sup>. In the late Eocene, K<sup>+</sup> content in the diagenetic medium increased significantly, and smectite began to transform into illite. From the early Eocene to the late Eocene, the overall climate and environmental characteristics showed a transition from cold and dry to a cold climate that alternated between dry and wet. The content changes of common oxides, such as CaO, MgO, K<sub>2</sub>O, Na<sub>2</sub>O, SiO<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub>, Fe<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub>, showed obvious correlation. Based on the content and ratio change tendencies of Sr, Ba, Cu, Zn, U, Th, Ce and other trace elements, combined with the variation characteristics of rare earth element contents, it is suggested that the Lulehe Formation was dominated by a dry and cold freshwater sedimentary environment, and that paleoclimatic conditions were relatively cold and arid during this sedimentary period. However, the climate in the sedimentary period of the Xiaganchaigou Formation was dominated by a cold environment alternating between dry and wet, which also reflected the finding that the global climate was mainly cold and dry in the early Eocene and gradually became warm and humid in the late Eocene. |
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| language | English |
| last_indexed | 2024-03-09T03:45:33Z |
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| spelling | doaj.art-7a0f31a445994f0197f734932c25246d2023-12-03T14:34:48ZengMDPI AGApplied Sciences2076-34172022-07-011214685010.3390/app12146850Eocene Sedimentary–Diagenetic Environment Analysis of the Pingtai Area of the Qaidam BasinGuoqiang Sun0Shuncun Zhang1Yetong Wang2Yaoliang Li3Hui Guo4Shangshang Bo5Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, ChinaNorthwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, ChinaNorthwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, ChinaNorthwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, ChinaNorthwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, ChinaNorthwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, ChinaBased on the petrological characteristics and elemental geochemical analysis of core samples from the Pingtai area in the northern structural belt of the Qaidam Basin, this study shows that the clay mineral assemblage of Lulehe Formation sandstone is dominated by high contents of smectite, chlorite and illite, and does not contain illite–smectite mixed layers or kaolinite. The chlorite and illite in the Xiaganchaigou Formation decreased gradually and the smectite disappeared. In addition, illite–smectite mixed layers began to appear and kaolinite was not present. These results indicate that the diagenetic environment of the Pingtai area in the early Eocene was dominated by alkaline media poor in K<sup>+</sup> and rich in Mg<sup>2+</sup>, Na<sup>+</sup> and Ca<sup>2+</sup>. In the late Eocene, K<sup>+</sup> content in the diagenetic medium increased significantly, and smectite began to transform into illite. From the early Eocene to the late Eocene, the overall climate and environmental characteristics showed a transition from cold and dry to a cold climate that alternated between dry and wet. The content changes of common oxides, such as CaO, MgO, K<sub>2</sub>O, Na<sub>2</sub>O, SiO<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub>, Fe<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub>, showed obvious correlation. Based on the content and ratio change tendencies of Sr, Ba, Cu, Zn, U, Th, Ce and other trace elements, combined with the variation characteristics of rare earth element contents, it is suggested that the Lulehe Formation was dominated by a dry and cold freshwater sedimentary environment, and that paleoclimatic conditions were relatively cold and arid during this sedimentary period. However, the climate in the sedimentary period of the Xiaganchaigou Formation was dominated by a cold environment alternating between dry and wet, which also reflected the finding that the global climate was mainly cold and dry in the early Eocene and gradually became warm and humid in the late Eocene.https://www.mdpi.com/2076-3417/12/14/6850clay mineralsmajor elementstrace elementssedimentary–diagenetic environmentQaidam Basin |
| spellingShingle | Guoqiang Sun Shuncun Zhang Yetong Wang Yaoliang Li Hui Guo Shangshang Bo Eocene Sedimentary–Diagenetic Environment Analysis of the Pingtai Area of the Qaidam Basin Applied Sciences clay minerals major elements trace elements sedimentary–diagenetic environment Qaidam Basin |
| title | Eocene Sedimentary–Diagenetic Environment Analysis of the Pingtai Area of the Qaidam Basin |
| title_full | Eocene Sedimentary–Diagenetic Environment Analysis of the Pingtai Area of the Qaidam Basin |
| title_fullStr | Eocene Sedimentary–Diagenetic Environment Analysis of the Pingtai Area of the Qaidam Basin |
| title_full_unstemmed | Eocene Sedimentary–Diagenetic Environment Analysis of the Pingtai Area of the Qaidam Basin |
| title_short | Eocene Sedimentary–Diagenetic Environment Analysis of the Pingtai Area of the Qaidam Basin |
| title_sort | eocene sedimentary diagenetic environment analysis of the pingtai area of the qaidam basin |
| topic | clay minerals major elements trace elements sedimentary–diagenetic environment Qaidam Basin |
| url | https://www.mdpi.com/2076-3417/12/14/6850 |
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