Samples of recent sediments may be analyzed directly for both carbonate carbon and organic carbon. To determine carbonate carbon, a mixture of sulfuric and phosphoric acids is added directly to the sediment sample. Adding a mixture of chromic and iodic acid and heating to 210 degrees C causes the conversion of organic carbon to carbon dioxide. A carrier gas is employed to transfer evolved gases through a series of liquid- and solid-phase absorption elements. Hydrogen chloride, hydrogen sulfide, and water vapor are removed sequentially before the carbon dioxide absorbs onto ascarite-magnesium perchlorate in a Schwartz-type tube. From the tube's increases in weight the carbonate carbon and the organic carbon are sequentially calculated. Each determination can be completed in less than 60 minutes. The technique has the advantages of low cost for equipment, accuracy, and applicability to a diversity of sediments, including clay- and carbonate-rich materials.