DOI: 10.1016/j.palaeo.2016.04.029
论文题名: Estimating the impact of early diagenesis on isotope records in shallow-marine carbonates: A case study from the Urgonian Platform in western Swiss Jura
作者: Godet A. ; Durlet C. ; Spangenberg J.E. ; Föllmi K.B.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2016
卷: 454 起始页码: 125
结束页码: 138
语种: 英语
英文关键词: Carbon and oxygen stable isotopes
; Cathodoluminescence
; Chemostratigraphy
; Early Cretaceous
; Meteoric eogenesis
; Northern Tethyan margin
英文摘要: The poor preservation of sedimentological and geochemical evidence often hampers the identification of subaerial exposure surfaces in carbonate platform successions. Such discontinuities may represent significant time gaps, justifying the quest for diagnostic indications. We investigated a lower Hauterivian to upper Barremian sedimentary succession from Switzerland to highlight the stratigraphic impact of meteoric diagenesis on platform carbonates. Petrographic observations revealed the presence of five generations of calcitic cements. Spot measurement of carbon and oxygen stable isotope compositions (δ13C and δ18O values, respectively) measurements relate them to specific diagenetic environments: selected blocky calcite cements exhibit an enrichment in light isotopes (12C, 16O), indicative of meteoric eogenesis, whereas very negative δ18O values link the last phase of cementation to mesogenesis. Meteoric calcitic cements formed during karstification of the top of the upper Barremian succession; burial diagenetic phases overlap these eogenetic phases, which thus cannot be related to recent telogenesis. We estimated the ratio of early meteoric versus burial cements within the studied succession: its stratigraphic repartition reveals that lower Aptian eogenesis influenced the geochemistry of platform carbonates as deep as 45 m below the exposure surface. In this interval, negative whole-rock δ13C values do not reflect contemporaneous variations of the δ13C curves documented in sections devoid of strong diagenetic impact. Such an impact is a function of the amount of meteoric cement filling pore space as well as of the primary carbon isotope composition of the carbonate sediments and of the meteoric cement. The vertical influence of a karst event is not restricted to the first metres directly below the exposure surface. Although meteoric diagenesis may not significantly alter microfacies, it may strongly perturb isotope systems. Building onto this case study, the application of δ13C chemostratigraphy to platform carbonates can only be performed with great caution and after a careful examination of diagenetic features. © 2015 . Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/68385
Appears in Collections: 过去全球变化的重建
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作者单位: Department of Geological Sciences, The University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX, United States; Institute of Earth Sciences, University of Lausanne, Anthropole, Lausanne, Switzerland; University of Bourgogne Franche-Comte, CNRS, Biogeosciences UMR 6282, Dijon, France; Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland
Recommended Citation:
Godet A.,Durlet C.,Spangenberg J.E.,et al. Estimating the impact of early diagenesis on isotope records in shallow-marine carbonates: A case study from the Urgonian Platform in western Swiss Jura[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2016-01-01,454