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Article Dans Une Revue Canadian journal of earth sciences Année : 2019

Strontium isotope geochemistry of modern and ancient archives: tracer of secular change in ocean chemistry

Amir Zaky
  • Fonction : Auteur
Uwe Brand
  • Fonction : Auteur
Dieter Buhl
  • Fonction : Auteur
Nigel Blamey
  • Fonction : Auteur
M. Aleksandra Bitner
  • Fonction : Auteur
Alan Logan
  • Fonction : Auteur
Daniele Gaspard
  • Fonction : Auteur
  • PersonId : 1128007
Alexander Popov
  • Fonction : Auteur

Résumé

Strontium isotopes of marine archives provide a significant means for tracing physical and chemical processes operating over geologic time. Modern articulated brachiopods and halite samples were collected from all depths of the world’s main water bodies. Material from the Arctic, North and South Atlantic, North and South Pacific, Indian and Southern oceans, as well as Caribbean and Mediterranean seas provide baseline parameters for diagenetic screening and reconstruction of seawater curves. The Sr isotopic ratio of modern brachiopods is unobscured by latitude, depth, and biologic factors (Order, valves, and shell segment). However, there is a small but significant impact of external sources reflected by salinity and temperature on the Sr isotope ratio of modern brachiopods. We found a significant difference in 87 Sr/ 86 Sr of brachiopods from polar and temperate-tropical habitats (p = 0.001), which should be considered when working with deep-time archives. The average 87 Sr/ 86 Sr value of all our modern shells (0.709160 ± 0.000019; N = 95) and halite (0.709153) is similar to values measured for modern seawater (0.710167 ± 0.000009; p = 0.118). The radiogenic Sr content of present-day seawater does not vary significantly, and modern biogenic-calcite 87 Sr/ 86 Sr ranges from 0.709126 to 0.709233 with a fluctuation of about ±0.000054. With the most rigorous diagenetic evaluations and stratigraphic assignment of deep-time samples, and applying the Sr isotope fluctuation recorded by modern biogenic calcite to ancient carbonates and a 1 Myr interval, reconstructions resulted in a seawater- 87 Sr curve with greater details during the Phanerozoic and Neoproterozoic.

Domaines

Paléontologie

Dates et versions

hal-03565940 , version 1 (11-02-2022)

Identifiants

Citer

Amir Zaky, Uwe Brand, Dieter Buhl, Nigel Blamey, M. Aleksandra Bitner, et al.. Strontium isotope geochemistry of modern and ancient archives: tracer of secular change in ocean chemistry. Canadian journal of earth sciences, 2019, 56 (3), pp.245-264. ⟨10.1139/cjes-2018-0085⟩. ⟨hal-03565940⟩
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