Stable carbon isotopic analysis of sedimentary organic matter by stepped combustion

A stepped combustion technique, incremental heating in oxygen, has been used to study the carbon isotopic composition of carbonaceous sediments. This technique can afford data on the organic matter of the sediment and can give information on the structure, namely the variations in the isotopic composition of different portions, of the kerogen. Green River shale has been used as a model material and results indicate that it contains two distinct carbonaceous components, a carbonate and kerogen. Isotopic compositions for the kerogen measured by stepped combustion closely match those obtained by normal methods following preconcentration of the kerogen by mineral removal and solvent extraction.The variation in isotopic composition with combustion temperature has been used to investigate relationships with maturity and to look at its use as a possible correlation tool.