Paleo-Redox Conditions of the Albian-Danian Carbonate Rocks of the Cauvery Basin, South India

Paleoredox Conditions of Paleocene to Miocene Rocks of Eastern Benin (Dahomey) Basin, Nigeria: Implications for Chemostratigraphy

“…The lower portions also recorded a positive shift close to 3ppm. Marine sediments deposited under oxic conditions are associated with low concentrations of U, whereas sediments from the anoxic to euxinic environments are high in U content (Jones & Manning, 1994;Madhavaraju et al, 2015). The observed concentrations of U in the upper 10 -25m points to oxic conditions while the lower parts suggest reducing conditions.…”

“…to the environments. The variations in the concentration of these elements and some redox-sensitive chemical elemental ratios serve as proxies to the prevalent paleo-redox conditions in both modern and ancient marine sediments (Madhavaraju et al, 2015). Significant paleoredox geochemical proxies include U, V, Mo, Co, Ni, V/Cr, V/Sc, U/Th, Th/U, V/(V+Ni) and Ni/Co (Ferriday & Montenari, 2016;Jones & Manning, 1994;Madhavaraju et al, 2015).…”

“…The variations in the concentration of these elements and some redox-sensitive chemical elemental ratios serve as proxies to the prevalent paleo-redox conditions in both modern and ancient marine sediments (Madhavaraju et al, 2015). Significant paleoredox geochemical proxies include U, V, Mo, Co, Ni, V/Cr, V/Sc, U/Th, Th/U, V/(V+Ni) and Ni/Co (Ferriday & Montenari, 2016;Jones & Manning, 1994;Madhavaraju et al, 2015). In a reducing marine environment, there is positive excursion of authigenic U principally in the sediment and not in the water column, because uranium is depleted from the water column and it is added to the sediment, while low U contents are ascribed to sediments deposited in oxygenated marine environments (Madhavaraju et al, 2015).…”

“…Significant paleoredox geochemical proxies include U, V, Mo, Co, Ni, V/Cr, V/Sc, U/Th, Th/U, V/(V+Ni) and Ni/Co (Ferriday & Montenari, 2016;Jones & Manning, 1994;Madhavaraju et al, 2015). In a reducing marine environment, there is positive excursion of authigenic U principally in the sediment and not in the water column, because uranium is depleted from the water column and it is added to the sediment, while low U contents are ascribed to sediments deposited in oxygenated marine environments (Madhavaraju et al, 2015). The U content in the uppermost sample (BH3) of well BH is higher (8.7ppm) than in the other parts of the well where there was a downward shift to about 1ppm in BH10 -BH25 and to around 3ppm from BH33 downhole (Figure 3a).…”

“…Positive excursions of vanadium (V) indicate oxic environments, as vanadium is relatively insoluble in oxic marine environment, which readily bounds to the sediments by surface adsorption processes and therefore accords a high concentration of V in the sediments (Madhavaraju et al, 2015). The V content in the upper 33m of well BH recorded lesser values (6-37ppm) than in the lower depths with higher concentrations (88 -171ppm) except for sample BH 137, which also has a low V content (18ppm).…”