title: On the origin of fiber calcite crystals in moonmilk deposits.
abstract: In this study, we show that moonmilk subaerial speleothems in Altamira Cave (Spain) consist of a network of fiber calcite crystals and active microbial structures. In Altamira moonmilks, the study of the typology and distribution of fiber crystals, extracellular polymeric substances, and microorganisms allowed us to define the initial stages of fiber crystal formation in recent samples as well as the variations in the microstructural arrangement in more evolved stages. Thus, we have been able to show the existence of a relationship among the different types of fiber crystals and their origins. This allowed us to outline a model that illustrates the different stages of formation of the moonmilk, developed on different substrata, concluding that microbes influence physicochemical precipitation, resulting in a variety of fiber crystal morphologies and sizes.
authors.affiliation: Unidad Asociada CSIC-UA, Laboratorio de Petrologia Aplicada, Departamento de Ciencias de la Tierra, Universidad de Alicante, Alicante, Spain.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Cañaveras
authors.forename: Soledad
authors.initials: S
authors.lastname: Cuezva
authors.forename: Sergio
authors.initials: S
authors.lastname: Sanchez-Moral
authors.forename: Javier
authors.initials: J
authors.lastname: Lario
authors.forename: Leonila
authors.initials: L
authors.lastname: Laiz
authors.forename: Juan Miguel
authors.initials: JM
authors.lastname: Gonzalez
authors.forename: Cesareo
authors.initials: C
authors.lastname: Saiz-Jimenez
mesh_terms: D001419:Bacteria / Q000648:ultrastructure; D018407:Bacterial Physiological Phenomena; D002119:Calcium Carbonate / Q000737:chemistry*; D005844:Geology / Q000379:methods; D019110:Meteoroids; D008903:Minerals / Q000032:analysis; D013030:Spain
chemical_list: D008903:Minerals; D002119:Calcium Carbonate