Microbial mat development and dolomite formation under pre-evaporitic conditions during the Atlantic in a temperate area: The Sarliève Lake (French Massif Central)

► Unusual dryness during the Atlantic favoured microbial growth in the Sarliève lake. ► Bacterial proliferation is evidenced by high amounts of regular and 2-Me hopanoids. ► An unknown hopanoid, with an extra methyl on ring D or E is also present. ► In these unusual conditions carbonates, including, dolomite, also precipitated. ► Despite marked changes, the medium remained anoxic during the Late Boreal-Atlantic.