Biogeochemistry of aragonite mad and oolites

Abstract

Aragonite needle mud and oolites from different localities contain a protein matrix comprised in large part of the acidic amino acids, aspartic and glutamic acid. At least one-third of the total organic matter is proteinaceous. The amino acid composition of the organic matter in all of the non-skeletal muds and oolites is nearly identical and is very similar to that in many skeletal carbonates. Treatment of samples with various oxidizing agents indicates that protein is within the non-skeletal carbonates and not just a coating on the outer surface. Adsorption experiments demonstrate that carbonate surfaces are able to selectively adsorb aspartic acid-rich protein. Based on the minor degree of amino acid diagenesis all muds and oolites appear to be essentially contemporaneous and not reworked. In terms of protein composition, skeletal and non-skeletal carbonates are virtually indistinguishable. In skeletal carbonates it is generally recognized that the protein matrix is an important aspect of the calcification process. Organic matter may also play an important role in the formation of oolites and aragonite needles.