Holocene beachrock has been studied on the northern and western shores of Bahiret el Biban, a shallow restricted lagoon in southeastern Tunisia. The beachrock consists of horizontal, cemented layers which are 2–15 cm thick. Early cementation took place at the water table below beach ridges, where geochemical, hydrodynamic and possibly also microbiological conditions favored rapid precipitation of aragonite and/or high-Mg calcite. Locally, superimposed low-Mg calcite cements point to subsequent freshwater influence. At one site, six vertically stacked beachrock beds are found. Total-rock ¹⁴C dating shows that the highest beachrock bed is older than the one (of the same petrographic composition) situated at the present groundwater level. This implies a downward progression of cementation which probably monitored the sea level fall following a local highstand about 3000 years ago.