Relación del índice de cristalinidad (IC) con la edad y el contenido de iones F y CO3 en muestras de vertebrados fósiles

Abstract

The crystalline fraction of enamel, dentin and metapodial bone of modern and fossil mammals were studied by X-ray diffraction analysis. The powdered samples were collected from several equids, giraffids, rhinocerotids and proboscideans of Spanish Neogene deposits. Changes in the crystallinity index (CI) of apatite are particularly useful to estimate later diagenetic changes in the fossil material. The enamel displays larger Cl than dentine and metapodial bone since they have a more dense structure; furthermore there is not a clear relationship between the Cl enlargement and the geological age of samples. In addition, the fluorine content increases during the fossilization process and accordingly the parameter CI increases in fossil samples. The carbonate enrichment is not linked to the age of the deposits; however this carbonate increase in enamel, dentine and metapodial bone reduces the CI parameter. The host sediments play an essential role in the crystallinity changes observed in fossil bones; e.g., in the silica sands case, samples display a high Cl while in the claystone and chalks case, they display a lower crystallinity index.