Origen and evolution of gypsum stromatolites in salars of the Andes highlands, northern Chile

Abstract

In several salars in the Andes Highlands in Chile, gypsum stromatolites have been described. Stromatolites are structures with organic origin and they are normally formed by carbonates. Field observations achieved in five salars in the Andes of northern Chile have permitted to recognize six stages during the gypsum stromatolites formation, from the growth of the organic mats to their almost disappearance by local erosive agents. The six stages are: 1) formation of the organic mat and start of the mineral structure development, 2) growth of the domes structure by trapping of gases in side of the organic mat, 3) development of the crystal gypsum wall , 4) death of the organic colony and exposition of the stromatolitic domes to the subaerial environment, 5) initial destruction of the dome structure and start of the central cavity filling and 6) final degradation of the structures and formation of the mounds with the gypsum crystals at the top.