The observation of palynological material from siliceous sediments needs separation and
isolation techniques, which include a preliminary chemical treatment to eliminate mineral phases. The
final residue, obtained after several treatments, is composed by a mixture of organic, vegetal and animal
materials. In some cases the presence of mineral phases such as crystalline phosphates formed during
the chemical attack is also confirmed. The elimination of these compounds from the palynological
materials is very important for an adequate observation, study and count under the optical microscope.
The aim of this work is to study and describe the newly formed phosphates during chemical treatment
and to formulate a valid method for its elimination without damage of the playnological material. Two
samples (Keuper facies, Upper Triassic) have been selected due to their content in the previously
described problematic phosphate phases. XRD, XRF and optical microscopy data show that the newly
formed phosphate phases, after the acid attack with HF (40% dissolution), are crandallite-gorceixite.
After several laboratory attempts, the elimination of the problematic phases has been made successfully
treating the samples with a final dissolution of HCl at 33%. All the morphological characteristics of the
palynological material have been preserved properly.
Resumen: La observacion del material palinologico procedente de sedimentos siliceos fosiles requiere tecnicas de separacion y aislamiento que incluyen un tratamiento quimico preliminar para la eliminacion de la mayor cantidad posible de fases minerales. Despues de los diversos tratamientos, el residuo obtenido contiene materiales organicos (vegetales y animales), en algun caso apatito y ocasionalmente, nuevas fases de fosfatos cristalinos formadas durante el ataque quimico. La eliminacion de estos ultimos compuestos es muy importante para la mejor observacion y estudio al microscopio del material palinologico. El objetivo de este trabajo es estudiar los fosfatos que se forman durante el tratamiento quimico y formular un metodo para su eliminacion sin alterar el contenido esporo-polinico. Se han seleccionado dos muestras de las facies Keuper (Triasico Superior) que presentan los problemas de formacion de fosfatos anteriormente descritos. Los analisis de DRX, FRX y microscopia optica realizados muestran que las nuevas fases formadas tras el ataque con disolucion de HF al 40% (utilizado para la eliminacion de los silicatos) son fosfatos de tipo crandallita-gorceixita. Tras varios ensayos, se ha tenido exito en la eliminacion de estos fosfatos neoformados mediante un ataque con disolucion al 33% de HCl que conserva todas las caracteristicas morfologicas del material palinologico. Palabras clave: eliminacion, formacion, fosfatos, palinologia, Triasico.