Post-mortem recrystallization of biogenic amorphous calcium carbonate guided by the inherited macromolecular framework.

In contrast to abiotically formed carbonates, biogenetic carbonates have been observed to be nanocomposite, organo-mineral structures, the basic build-blocks of which are particles of quasi-uniform size (10-100 nm) organized into complex higher-order hierarchical structures, typically with highly controlled crystal-axis alignments. Some of these characteristics serve as criteria for inferring a biological origin and the state of preservation of fossil carbonate materials, and to determine whether the biomineralization process was biologically induced or controlled. Here we show that a calcium storage structure formed by the American lobster, a gastrolith initially consisting of amorphous calcium carbonate (ACC) and amorphous calcium phosphate (ACP), post-mortem can crystallize into (thus secondary) calcite with structural properties strongly influenced by the inherited organic matrix.

Earthworm granules: A model of non-classical biogenic calcium carbonate phase transformations.

Different non-classical crystallization mechanisms have been invoked to explain structural and compositional properties of biocrystals. The identification of precursor amorphous nanoparticle aggregation as an onset process in the formation of numerous biominerals (crystallization via particle attachment) constituted a most important breakthrough for understanding biologically mediated mineralization. A comprehensive understanding about how the attached amorphous particles transform into more stable, crystalline grains has yet to be elucidated.

Diagenetic and Biological Overprints in Geochemical Signatures of the Tertiary Layer (Brachiopoda): Assessing the Paleoclimatic Interpretation.

Variations in the geochemical signatures of fossil brachiopod shells may be due to diagenesis and/or biological processes (i.e., 'vital effects').

Strong links between Saharan dust fluxes, monsoon strength, and North Atlantic climate during the last 5000 years.

Despite the multiple impacts of mineral aerosols on global and regional climate and the primary climatic control on atmospheric dust fluxes, dust-climate feedbacks remain poorly constrained, particularly at submillennial time scales, hampering regional and global climate models. We reconstruct Saharan dust fluxes over Western Europe for the last 5000 years, by means of speleothem strontium isotope ratios (Sr/Sr) and karst modeling. The record reveals a long-term increase in Saharan dust flux, consistent with progressive North Africa aridification and strengthening of Northern Hemisphere latitudinal climatic gradients.