“…Secular changes in the loci of Phanerozoic chert deposition refl ect the evolution and ecology of silicifying organisms Schubert et al, 1997;Kidder and Erwin, 2001;Kidder and Mumma, 2003). In modern ocean basins, diatoms quantitatively control the removal of silica, maintaining silica concentrations in the oceans (surface water generally <2 μM, deep water ~100 μM) far below saturation with respect to amorphous silica (~1000 μM).…”