Mesocrystalline Architecture in Hyaline Foraminifer Shells Indicates a Non‐Classical Crystallisation Pathway

Abstract

Calcareous foraminifers are an abundant group of planktic and benthic marine unicellular organisms, which together constitute an important component of the global carbon cycle (Langer, 2008;Schiebel, 2002). Foraminifer shells (tests) can resist dissolution and diagenesis over millions of years, and hence provide an outstanding archive for climate reconstruction at high time resolution from sediment cores, which is possible via empirical calibration of chemical or physical characteristics of the shells of recent species (e.g., Fischer & Wefer, 1999;Katz et al., 2010). Despite their importance as a paleoclimate archive, the biomineralization of foraminifers is not mechanistically understood in detail, which leaves the fundamental relationship between environmental parameters and proxy data enigmatic. For example, the possible presence of residues of metastable carbonate phases such as vaterite was only recently discovered (Jacob et al., 2017), and the delivery of ions to the biomineralization site is an ongoing topic of debate (

Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration

“…In this contribution we define a grain as a domain of similar crystallographic orientation surrounded by a grain boundary with >10° orientation change between adjacent grains. These grains are typically synonymous with previously identified "mesocrystals" (Yin et al, 2021;Arns et al, 2022); and are composed of numerous small crystals of similar size and shape (in this case, the sub-micron microgranules of biogenic foraminiferal calcite). Some of the key findings of previous EBSD investigations into biomineralisation processes include: 1) the "mesocrystal structure" of units of similarly oriented https://doi.org/10.5194/egusphere-2023-2213 Preprint.…”

“…nanometer scale microgranules; 2) the preferred alignment of the calcite c-axis perpendicular to the test wall, which is thought to be induced by biopolymers of the primary organic sheet (POS); and 3) the presence of 60° twinning in test calcite (e.g. Pabich, Vollmen and Gussone, 2020;Yin et al, 2021;Arns et al, 2022;Lastam et al, 2023 a,b ).…”

Guidelines derived from biomineralized tissues for design and construction of high-performance biomimetic materials: from weak to strong

“…This non-classical crystallization mechanism, especially involving the amorphous precursor pathway, although somewhat controversial, has been supported experimentally directly or indirectly. 183,220,[346][347][348][349][350][351] In the case of the classical nucleation process, the Gibbs free energy is the nucleation barrier (Fig. 22).…”

“…This non-classical crystallization mechanism, especially involving the amorphous precursor pathway, although somewhat controversial, has been supported experimentally directly or indirectly. 183,220,346–351…”

Single chamber Mg/Ca analyses of Globigerinoides ruber for paleo-proxy calibration using femtosecond LA-ICP-MS

“…These marine protozoans live in the surface to sub-thermocline layer of the open ocean and deep marginal seas 1 . Their shell usually consists of low-Mg calcite layers orientated in a radial structure (Arns et al, 2022, and references therein) 19 .…”