Extant shore-platform stromatolite (SPS) assemblage

Abstract

Abstract. Extant peritidal, micritic stromatolites and tufa are growing discontinuously along the southeast African Indian 15Ocean rocky peritidal zone. Microbialites are ubiquitous on this coast but only calcify when carbonate rich groundwater is present; if horizontal surfaces (shore platforms) are present stromatolites develop, if vertical surfaces are present tufa forms.Tufa and stromatolites are end members of a spectrum dictated by coastal topography. Extant shore-platform stromatolites (SPS) occur in very high wave energy settings, often around headlands, boulder beaches and/or beach ridges, storm swashterraces and coastal dunes. Stromatolite growth is seen on soft coastlines but the preservation potential is very low/ zero. SPS 20 are produced by mineral precipitation, not trapping and binding. SPS are developing in a mildly transgressive siliciclastic setting. Laminar and colloform stromatolite morphologies could be preserved in the geological record as micritic lenses on a palaeo-shore platform surface. SPS share many features with Precambrian stromatolites. Terraces associated with oceanic or lacustrine flooding surfaces should not be ignored when searching for potential stromatolite deposits on Mars. 25