![]() Mossbauer spectroscopy reflects a minor substitution of Al 3þ-Fe 3þ (total) in tetrahedral sites and significant substitution of the same in octahedral sites. XRD, FEG-SEM and spectroscopy of glauconite pellets indicate an 'evolved' stage of maturation. ![]() ![]() Unlike most Phanerozoic examples, Ukra glauconite forms by the variable degree of replacement of quartz, feldspar and mica grains. The concentration of glau-conite steadily increases towards the maximum flooding surface, maximizing around 50%, and sharply falls at the onset of progradation. Glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf. An integrated study involving sedimentology, mineral chemistry and spectroscopy highlights a distinctive compositional evolution of Cretaceous glauconite within the Ukra Hill Member.
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