Fossilization in Geopark Araripe studied through X-ray diffraction,   scanning microscopy and thermogravimetric analysis
  The Geopark Araripe, located in Northeastern Brazil, is the first UNESCO Natural Park in the South hemisphere and a world-famous fossil deposit of the Early Cretaceous period (approximately 120 million years). Fossilized fish fauna in Geopark Araripe is found inside of sedimentary rocks in three-dimensional forms. In the present study sedimentary rocks and fossil fish Rhacolepis bucalis have been carefully analysed by means of X-ray powder diffraction, scanning electron microscopy and termogravimetric analysis. Mineralogical composition of the fossil fish was explained in terms of facts occurred at the initial stages of the opening of the South Atlantic and the oceanic hydrothermal phenomena (``black smoker'', ``white smoker'' and warm-water events). The occurrence of organic substance was, for the first time, evaluated in collapsed internal elements (intestinal and muscles) by termogravimetric analysis. 
Ricardo J. C. Lima, Paulo T. C. Freire, Z\'elia S. Macedo, Jos\'e M.   Sasaki, Ant\^onio A. F. Saraiva