Organic carbon, sulphur, 13Corg, iron, manganese and calcium have been measured across a subsurface-weathering front in Pliocene sediments in southern Sicily. The results show an almost quantitative removal of Corg and sulphur and an increase in iron and manganese oxides over the weathering front, accompanied with a significant shift of the 13Corg to lower values. These data are among the first to support the rapid, extensive weathering of sedimentary organic matter and sulphur, a basic assumption made in global biogeochemical models on a Phanerozoic timescale. ; Organic carbon, sulphur, 13Corg, iron, manganese and calcium have been measured across a subsurface-weathering front in Pliocene sediments in southern Sicily. The results show an almost quantitative removal of Corg and sulphur and an increase in iron and manganese oxides over the weathering front, accompanied with a significant shift of the 13Corg to lower values. These data are among the first to support the rapid, extensive weathering of sedimentary organic matter and sulphur, a basic assumption made in global biogeochemical models on a Phanerozoic timescale.