DOI: 10.1007/s00531-012-0845-5
Scopus记录号: 2-s2.0-84878107319
论文题名: Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils
作者: Kocsis L. ; Ounis A. ; Chaabani F. ; Salah N.M.
刊名: International Journal of Earth Sciences
ISSN: 14373254
出版年: 2013
卷: 102, 期: 4 起始页码: 1111
结束页码: 1129
语种: 英语
英文关键词: Oxygen isotope
; Paleocene-Eocene
; Phosphate
; Shark teeth
; Strontium isotope stratigraphy
; Tunisia
Scopus关键词: basin evolution
; carbonate
; coprolite
; fossil
; geochemistry
; Maastrichtian
; oxygen isotope
; Paleocene-Eocene boundary
; paleoenvironment
; phosphate
; phosphorite
; sea level
; shark
; stratigraphy
; strontium isotope
; tooth
; Gafsa
; Tunisia
; Chondrichthyes
英文摘要: Fossil shark teeth and coprolites from three major phosphorite occurrences in the Gafsa Basin (southwestern Tunisia) were investigated for their geochemical compositions to improve local stratigraphy and to better assess paleoenvironmental conditions. 87Sr/86Sr isotope ratios of shark teeth from the Early Maastrichtian El Haria Formation and from the Early Eocene Métlaoui s.s. Formation yielded Sr isotope ages of 68 ± 1 and 47.9 ± 1.3 Ma, respectively, which accord with the expected stratigraphic positions of these sediments. Conversely, shark teeth from the Paleocene-Eocene Chouabine Formation have large variation in Sr isotope ratios even within individual layers. After statistical treatment and then elimination of certain outlier samples, three age-models are proposed and discussed. The most reasonable solution includes three subsequent Sr ages of 61.8 ± 2.2 Ma, 57.2 ± 1.8 and 54.6 ± 1.6 for layer IX, layers VIII-V and layers IV-0, respectively. Three scenarios are discussed for explanation of the presence of the outliers: (1) diagenesis, (2) re-working and (3) locally controlled seawater Sr isotope ratio. The most plausible account for the higher 87Sr/86Sr ratios relative to the global ocean in some fossils is enhanced intrabasinal re-working due to low sea level. Conversely, the sample with lower 87Sr/86Sr than the global seawater may link to diagenesis or to seawater influenced by weathering of Late Cretaceous marine carbonates, which latter is supported by model calculation as well. The εNd values of these fossils are very similar to those reported for Paleogene and Late Cretaceous Tethyan seawater and are compatible with the above interpretations. The relatively low oxygen isotope values in shark teeth from the topmost phosphate bed of the Chouabine Formation, together with the Sr isotope results, point toward recovering better connections with the open sea. These δ18O data reflect elevated ambient temperature, which may link to the Early Eocene Climatic Optimum. © 2012 Springer-Verlag Berlin Heidelberg. URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878107319&doi=10.1007%2fs00531-012-0845-5&partnerID=40&md5=47d4da1e2c8eef13a14868aee120bec9
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/70554
Appears in Collections: 影响、适应和脆弱性 气候减缓与适应
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作者单位: UNIL-GEOPOLIS, Institute of Earth Sciences, Université de Lausanne, 1015 Lausanne, Switzerland; Laboratoire des Ressources Minérales et Environnement Faculté des Sciences de Tunis, Université de Tunis El Manar, Tunis, Tunisia; Direction de Géologie, Compagnie des Phosphates de Gafsa, Métlaoui, Tunisia
Recommended Citation:
Kocsis L.,Ounis A.,Chaabani F.,et al. Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils[J]. International Journal of Earth Sciences,2013-01-01,102(4)