DOI: 10.1016/j.quascirev.2016.06.020
Scopus记录号: 2-s2.0-84978289042
论文题名: “Cryptic” diagenesis and its implications for speleothem geochronologies
作者: Bajo P. ; Hellstrom J. ; Frisia S. ; Drysdale R. ; Black J. ; Woodhead J. ; Borsato A. ; Zanchetta G. ; Wallace M.W. ; Regattieri E. ; Haese R.
刊名: Quaternary Science Reviews
ISSN: 2773791
出版年: 2016
卷: 148 起始页码: 17
结束页码: 28
语种: 英语
英文关键词: Micro-CT
; Outliers
; Petrography
; Speleothems
; U-loss
; U-Th dating
Scopus关键词: Computerized tomography
; Petrography
; Sedimentology
; Statistics
; Stratigraphy
; Uranium
; Causative mechanisms
; Diagenetic alteration
; Micro CT
; Outliers
; Palaeoclimate archives
; Reproducibilities
; Speleothems
; Stratigraphic sequences
; Climate change
; aragonite
; diagenesis
; formation mechanism
; geochronology
; paleoclimate
; petrography
; speleothem
; stalagmite
; tomography
; uranium
; uranium series dating
; Corchia Cave
; Italy
; Lucca
; Tuscany
英文摘要: Speleothems are usually considered as one of the most amenable palaeoclimate archives for U-series dating. A number of studies in recent years, however, report cases of diagenetic alteration which compromises the use of U-series systematics in speleothems, resulting in inaccurate U-Th ages. Here we present the results of a high-resolution U-Th dating study of a stalagmite (CC26) from Corchia Cave in Italy where we document a number of departures from an otherwise well-defined age-depth model, and explore potential causes for these outliers. Unlike examples illustrated in previous studies, CC26 contains no visible evidence of neomorphism, and appears, at least superficially, ideally suited to dating. Good reproducibility obtained between multi-aliquot U-Th analyses removes any possibility of analytical issues contributing to these outliers. Furthermore, replicate analyses of samples from the same stratigraphic layer yielded ages in stratigraphic sequence, implying very localized open-system behavior. Uranium loss is suggested as a causative mechanism on account of the fact that all the outliers are older than their assumed true age. A limited number of micro-voids were observed under micro-CT analyses, and it is proposed that these were pathways for U loss. Uranium-loss modelling allows us to constrain the possible timing of diagenetic alteration and indicates that the precursor for the outlier with the largest age discrepancy (309%) must have been aragonite. This study indicates that visibly unaltered speleothems may still contain small domains that have experienced post-depositional alteration. Such “cryptic” diagenesis, as recorded in this stalagmite, has implications for the constancy of accuracy of the U-series dating technique, and suggests a need for careful examination of speleothems prior to dating, particularly in low-resolution U-Th studies. © 2016 Elsevier Ltd Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/59477
Appears in Collections: 过去全球变化的重建
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作者单位: School of Geography, University of Melbourne, Australia; School of Earth Sciences, University of Melbourne, Australia; School of Environmental and Life Sciences, University of Newcastle, Australia; Department of Earth Sciences, University of Pisa, Italy; Institute of Environmental Geology and Geoengineering, IGAG-CNR, Rome, Italy
Recommended Citation:
Bajo P.,Hellstrom J.,Frisia S.,et al. “Cryptic” diagenesis and its implications for speleothem geochronologies[J]. Quaternary Science Reviews,2016-01-01,148