Loss on ignition:: a qualitative or quantitative method for organic matter and carbonate mineral content in sediments?

Since the publication of the paper of Dean (1974), loss on ignition (LOT) has been widely used as a method to estimate the amount of organic matter and carbonate mineral content (and indirectly of organic and inorganic carbon) in sediments. The relationships between LOI at 550 degreesC (LOI550) and organic carbon (OC) content and between LOI at 950 degreesC (LOI950) and inorganic carbon (IC) content are currently accepted as a standard. However, the comparison of 150 analyses of samples of diverse lithologies, collected from a single core, reveals that these relationships are affected by sediment composition (presence of clays, salts, and the variable content of organic carbon). This results in an incremental error on the estimation of carbon content from LOI values that invalidates the use of LOI values as a quantitative method for estimating carbon content. Conversely, the general trends of LOI550 and LOI950 show a good correlation with carbon content (both organic and inorganic) allowing use of LOI as a qualitative test for carbon content. Similarly, in our case, LOI at 105degreesC (LOI105) is a good qualitative proxy for the trends in gypsum content.