Resumen de Palaeoredox link with the late Neoproterozoic–early Cambrian Bilara carbonate deposition, Marwar Supergroup, India
A. H. Ansari, S. K. Pandey, Kamlesh Kumar, Shailesh Agrawal, Shamim Ahmad, Mayank Shekhar
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.
