Calcium biomineralizations and bioerosion, associated to bioclastic deposits in coastal sequences of the southeastern pampean plain, argentina

OSTERRIETH L. MARGARITA; FRAYSSINET, CELIA; FRAYSSINET, LUCRECIA

Simposio; The 14th International Symposium on Biomineralization (BIOMIN XIV) From Molecular and Nano-structural Analyses to Environmental Science; 2017

Calcium biomineralizations are produced by microorganisms (bacteria, algae, fungi,actinomycetes), plants and animals. Calcite, vaterite and aragonite are the major mineralsin animals, whereas in plants, calcium oxalate is the most representative. Bioerosion isanother process associated to biomineralizations; it occurs due to the dissolution or erosionof the surface of minerals, to fissures, and to the drilling of minerals and/or biominerals.The site under study is located in the coastal areas of Mar Chiquita, Buenos Aires province(34°-39° S and 57°-63° W), in pedo-sedimentary sequences of the coastal plains. Disturbedand undisturbed samples were studied at different scales of resolution: mesoscopic,microscopic and submicroscopic, using optical microscopy SEM/EDX. In Calcic soils, thebioclasts are affected by bioerosion through the action of microorganisms and subsequentlycalcium reprecipited as secondary oxalates and carbonates biomineralizations. Thesebiomineralizations also add or weakly bind skeletal components, incorporating themselvesinto the matrix of soil and sediments. Mineralo-chemical studies confirm the presenceof calcium and varying carbon contents, depending on the stage of development of thecrystals. Thus, it was possible to define the genetic sequence of calcite via calcium oxalate(weddellite and whewellite) associated with hyphae, algae, soil bacteria, and actinomycetes.A remarkable variety of dichotomous tubes was found, as clear evidence of fungal origin,in addition to elongated tubes of multiple sizes and diameters, and complex interdigitatedcrystalline textures of oxalate and calcium carbonates. The type and diversity of calciumbiomineralizations increase directly in relation with time and pedogenetic evolution and aregood mineralo-biochemical indicators for a better understanding of both current and pastpedological environmental processes. These biomineralizations have been determinant inthe origin, evolution, and resistance to natural and anthropic degradation of the Holocenepedo-sedimentary sequences of coastal plain, Buenos Aires province, Argentina