Distribution and geochemical significance of amino acids and amino sugars in a clay suite of the Pliocene-Pleistocene age from central Italy

• Published in: Organic geochemistry Vol. 9; no. 3; pp. 127 - 133
• Main Authors: Belluomini, G., Branca, M., Calderoni, G., Schnitzer, M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1986; Elsevier Science
• Subjects: absence of aromatic and S-containing amino-acids; amino acid-clay complexes; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochemistry; reducing conditions; Soil and rock geochemistry; stability of serine; sulfide sulfur; reducing conditions; absence of aromatic and S-containing amino-acids; amino acid-clay complexes; stability of serine; sulfide sulfur; Neogene; Clay; Organic carbon; Complexation; Carbohydrates; Complexing; Quaternary; Europe; Tertiary; Amino acids; Nitrogen; Pliocene; Clastic sediments; Sedimentary rocks; Italy; Sulfur; Sugar; Latium; Pleistocene
• ISSN: 0146-6380; 1873-5290
• DOI: 10.1016/0146-6380(86)90102-6

Six samples from a Pliocene-Pleistocene clay sequence were analyzed for total nitrogen, total and reduced sulfur, organic carbon, amino acids and amino sugars. Organic carbon decreased with depth but total nitrogen and sulfur exhibited irregular vertical distributions. Both amino acids and amino sugars did not occur in free, water-soluble or carbonate-associated forms; strong acid hydrolysis was required for their release. Their complete recovery was achieved only after HF pretreatment of the samples, indicating close association of some amino compounds with clays. The relative distribution of amino acid types was fairly regular throughout the whole series. Neutral amino acids ( X = 66% ) were the most abundant ones. Basic and acidic amino acids accounted for about 24 and 11%, respectively, of the total amino acids; aromatic amino acids were highly depleted and sulfur-containing amino acids were absent. The most striking feature of the organic matter contained in the clay suite was its low protein or peptide content, suggesting intensive diagenetic degradation throughout geologic times leading to the formation of kerogene-like compounds. N in amino-compounds in these sediments accounted only for 0.09–0.72% of the total N, compared to 30% for the average agricultural soil organic matter.