Abstract The initial acquisition of calcium carbonate polymorphs (aragonite and calcite) at the onset skeletal biomineralization by disparate metazoans across Ediacaran-Cambrian transition is thought to be directly influenced Earth's seawater chemistry. It has been presumed that animal clades first acquired mineralized skeletons during so-called “aragonite sea” latest Ediacaran earliest Cambria...

The Ediacaran–Cambrian Radiation marks the widespread appearance of metazoans and calcareous biomineralised hard parts. These innovations occurred during an interval dynamic changes in marine redox sea water chemistry. Here, changing carbonate mineralogy, Mg/Ca ratios rare earth element concentrations including relative abundance cerium (Ce anomaly: Ceanom) are documented to track oxygen levels...

Similar carbonate fabrics may result from different pathways of precipitation and diagenetic replacement. Distinguishing the underlying mechanisms leading to a given fabric is relevant, both in terms an environmental interpretation. Prominent among are aragonite botryoids spherulites, typically interpreted as direct seawater precipitates used proxies for fluid properties depositional environmen...

We found direct evidence that a single-crystal-like aragonite platelet is essentially assembled with aragonite nanoparticles. The aragonite nanoparticles are readily oriented and assembled into pseudo-single-crystal aragonite platelets via screw dislocation and amorphous aggregation, which are two dominant mediating mechanisms between nanoparticles during biomineralization. The heat treatment b...

We reveal that the aragonite CaCO3 platelets in nacre of Haliotis laevigata are covered with a continuous layer of disordered amorphous CaCO3 and that there is no protein interaction with this layer. This finding contradicts classical paradigms of biomineralization, e.g., an epitaxial match between the structural organic matrix and the formed mineral. This finding also highlights the role of ph...