Gypsum deposits in the Carpathian Foredeep of southern Poland were altered daring burial to anhydrite. This alteration did not completely destroy primary lithologic features. Different gypsum lithotypes have equivalents in the altered sulfate sections. Relics of, and pseudomorphs after, crystalline and sedimentary structures indicate that extensive replacement and cementation occurred early during burial diagenesis. The replacement of gypsum by anhydrite was probably initiated in the shallow subsurface by high temperature and/or reaction with brines of high salinity. Accordingly, the importance of a deep burial for gypsum diagenesis in the studied area may have been overestimated.