INTERACTION BETWEEN CALCIUM-CARBONATE AND ORGANIC-MATTER - AN EXAMPLE FROM THE ROSSO AMMONITICO VERONESE (VENETO, NORTH ITALY)

The contents of free and combined amino acids from the Rosso Ammonitico Veronese Formation, determined with an autoanalyzer and expressed in R (residues)/1000, are compared with some data in the literature on limestones with similar stromatolitic structures (Gannat Limestone - Oligo-Miocene), marine plankton and Recent marine sediments. The type of organic matter (prevalence of basic and neutral over acid amino acids) suggests that the appearance and type of some sedimentary and/or early diagenetic structures (stromatolitic laminations, nodularity, cementation and dissolution structures) are controlled by the interactions between the organic matter (in particular amino acids) and the different calcium carbonate phases. The prolonged absence of cementation in some layers and the repeated events of dissolution found in others may have been two of the causes why the Rosso Ammonitico Veronese is such a condensed formation.