Guttulatic calcite: A carbonate microtexture that reveals frigid formation conditions

Abstract The paragenesis of carbonate pseudomorphic textures in the rock record that are inferred to represent replaced metastable ikaite (CaCO3·6H2O), which forms at frigid temperatures, is uncertain. Petrographic analysis Mono Lake (California, USA) Pleistocene tufas allowed recognition a distinctive calcite microtexture, termed guttulatic calcite, during dehydration and diagnostic for precursor ikaite. texture characterized by pseudo-hexagonal or spherical low-Mg cores, likely formed initially as vaterite, with an ellipsoidal overgrowth, secondary high-Mg sparry micritic cement. Observations pseudomorphs, combined review more ancient examples, indicate records can be used infer paleotemperatures.