DOI: 10.1016/j.palaeo.2017.05.027
论文题名: High-resolution clay mineral and major elemental characterization of a Permian-Triassic terrestrial succession in southwestern China: Diagenetic and paleoclimatic/paleoenvironmental significance
作者: Xu G. ; Feng Q. ; Deconinck J.F. ; Shen J. ; Zhao T. ; Young A.L.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2017
卷: 481 起始页码: 77
结束页码: 93
语种: 英语
英文关键词: Acidification
; Chemical index of alteration (CIA)
; Chemical weathering decrease
; Diagenesis
; Drying-out
; Vermiculite
英文摘要: Relatively high-resolution clay mineralogical and chemical index of alteration (CIA) analyses were conducted on the terrestrial Lubei section in southwestern China, to gain a better understanding of the paleoclimatic/paleoenvironmental evolution on land during the Permian-Triassic transition (P-Tr transition). Clay-mineral species include illite-smectite mixed layers (I/S), illite, irregular chlorite-expandable mixed layers (C/E), chlorite, kaolinite, vermiculite, hydroxyl-interlayered mineral (HIM), and corrensite. CIA values are as high as approaching 100 in the Permian and show a gradual and subtle decrease towards the lowermost Triassic, where a sudden decrease to persistently < 60 occurs with only periodic positive excursions. Diagenetic alteration is important at the study section and include chloritization, illitization of smectite in the Permian-lowest Triassic, transformation of smectite to corrensite in the upper sampled Triassic and potassium-addition induced decrease of CIA values throughout the section. However, with the integration of climate-sensitive sedimentary features, paleoclimatic/paleoenvironmental information was extracted from both clay-mineral composition and CIA. The dominance of precursor smectite together with the occurrence of kaolinite, Gigantopteris-type flora and coal seams, indicates an overall warm and semi-humid to semi-arid climate for the Permian part, and a general drying-out trend is suggested by the gradual decrease and final disappearance upsection of kaolinite, Gigantopteris-type flora and coal seams, as well as decreasing CIA values. Chemical weathering decrease is minor up to the lowest Triassic, which is mainly manifested by the subtle decrease of CIA values and which is probably partly due to the augmentation by acidification as indicated by the presence of vermiculite and HIM clay minerals. The short-term lingering (preliminarily estimated as < 0.08 Myr) of relatively intense chemical weathering after the extinction event was followed by an abrupt drop of CIA values to < 60, which indicates the onset of a rapid and enhanced dry-out condition unfavorable for chemical weathering. In association with the general drying-out trend is an increase in climate periodicity and/or seasonality, which is manifested by increasingly prominent laminations, lithological alternation and intermittent large excursions of CIA values, suggesting a more complicated climate condition during the Early Triassic than previously recognized. While drying-out rather than acidification is suggested in this study to have been a killer agent to land plant at the Lubei section, the real relationship between environmental deterioration and the end-Permian mass extinction is still enigmatic and needs further investigation. This is the first relative high-resolution clay mineralogical and CIA investigation on a well-preserved and continuous terrestrial Permian-Triassic section. © 2017 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/67797
Appears in Collections: 过去全球变化的重建
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作者单位: State Key Laboratory of Geological Processes and Mineral Resources, China University of GeosciencesHubei, China; Biogéosciences, UMR 6282, CNRS, Univ. Bourgogne Franche-Comté, 6 Boulevard Gabriel, Dijon, France; School of Earth Science, China University of GeosciencesHubei, China; Department of Geology, University of Cincinnati, Cincinnati, OH, United States
Recommended Citation:
Xu G.,Feng Q.,Deconinck J.F.,et al. High-resolution clay mineral and major elemental characterization of a Permian-Triassic terrestrial succession in southwestern China: Diagenetic and paleoclimatic/paleoenvironmental significance[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2017-01-01,481