Radiaxial-fibrous calcites: A new look at an old problem

摘要: Abstract Marine radiaxial-fibrous and fascicular-optic calcites are very common but poorly understood pore-filling cements in Paleozoic Mesozoic marine neritic upper bathyal limestones. The main diagnostic feature of these is their converging or diverging crystal c-axis, respectively. reasons for this anomalous texture at present unknown. Another controversy due to the relative lack occurrences Cenozoic strata apparent absence Quaternary Despite uncertainties, fibrous thought by some be amongst best proxies geochemistry ancient oceans because metabolic effects during precipitation. Applying electron backscatter diffraction analysis, we here first time document subordinate biominerals from well-preserved Jurassic Cretaceous low-Mg calcite belemnite rostra. finding biogenic combination with recent description Holocene modern stalagmites represents—in view authors—a significant advance carbonate research. Here, findings placed wider, processes-oriented context significance speloan counterparts assessed. Comparing physico-chemical organomineralic properties different precipitation sites indicates that variations c-axis orientation not related a specific nucleation environment substratum. In contrast, preliminary crystallographic analyses suggest kinetic factors subtle gradients statistical replacements Ca 2+ Mg structure may lead local strain resulting c-axes.