Organotemplate silica deposition in Neoproterozoic deep-marine environments: Evidence from the Penganga Group, Adilabad, India

Silica in bedded cherts interstratified with manganese carbonates in a deep-water carbonate ramp succession of the Neoproterozoic Penganga Group, India, displays film-like, spherical to rod-shaped, and tubular branching microstructures. The microstructures resemble mineralized extracellular polysaccharides, biofilms and bacterial morphologies. The microstructures suggest silicification by nucleation of silica on organic-templates or indirectly as sorbed species accumulating on organic templates. Given that similar microstructures have also been documented in Archean cherts it is proposed that organotemplates might have been an important sink for the deposition of silica in Precambrian deep-water marine environments.