Distinguishing biogenic carbonates
Distinguishing biogenic carbonates
Biogenic minerals (biominerals) differ in structure and biogeochemical composition from their abiotic counterparts. Until now, it was believed that diagenetic changes in biominerals lead to the loss of most features indicative of their biogenic nature. In the published paper, we demonstrate that in the American lobster structures formed by amorphous calcium carbonate can crystallize post-mortem into calcite. The crystallization process is influenced by the inherited organic matrix, resulting in secondary calcite that meets some structural criteria for biominerals. Our observations help distinguishing biogenic carbonates.
Figure: The mature gastrolith of the American lobster is originally composed of dozens of columnar units of amorphous calcium carbonate with a layered, nanogranular structure (left panel). One of the diagenetically altered (calcite) columnar units exhibits a complex, hierarchical structure with a braid-like microstructure and granular nanostructure (right panel).