Palaeoredox link with the late Neoproterozoic–early Cambrian Bilara carbonate deposition, Marwar Supergroup, India

• A. H. Ansari ^[1] ; S. K. Pandey ^[1] ; Kamlesh Kumar ^[1] ; Shailesh Agrawal ^[1] ; Shamim Ahmad ^[1] ; Mayank Shekhar ^[1]
  1. [1] Birbal Sahni Institute of Palaeosciences
• Localización: Carbonates and Evaporites, ISSN 0891-2556, Vol. 35, Nº. 2, 2020
• Idioma: inglés
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• Resumen

  • This study performed a stable isotope and redox-sensitive trace-element investigation on the Gotan Limestone and Pondlo Dolomite of the Bilara Group, Marwar Supergroup to decipher the palaeodepositional redox condition. A multivariate-statistical analysis of geochemical data set (δ13C-carb, δ18O-carb, δ13C-org, TOC, V, Ni, Cu, Zn, Mo, Pb, and U) reveals that limestone and dolomite units of the Bilara Group were deposited under two different redox regimes. Dolomite has an average δ13C-org values ~ − 30.0 ‰ and shows a statistically significant negative correlation with δ13C-carb which indicates an oxygen-depleted closed palaeodepositional environment. Dolomite δ13C-carb also shows a statistically significant negative correlation with redox-sensitive trace elements V, Ce, Pb, and U which infer higher secondary productivity during the dolomite deposition. The limestone has an average δ13C-org values ~ − 28.9 ‰ and δ13C-carb shows a significant positive correlation with δ18O-carb and Sr, whereas δ13C-carb shows a significant negative correlation with V and U. These statistical relationships among the geochemical parameter are indicative of suboxic-to-oxic water column with a relatively higher depth that received a significant input of water discharge from the terrestrial region. This discharge may have brought nutrients and other weathering-derived ions into the basin.