“…Diagenetic alteration of sedimentary amino acids was assessed using the Degradation Index (DI) developed by Dauwe and Middelburg (1998) and Dauwe et al (1999). This index is based on the first axis of a Principal Component Analysis (PCA) of the amino acid composition and summarizes, in one variable, the relative cumulative variation of 14 amino acids (aspartic acid, glutamic acid, serine, histidine, thréonine, arginine, glycine, tyrosine, alanine, méthionine, valine, phenylalanine, isoleucine and leucine).…”