How Do Fossilized Mammalian Bones Behave During Chemical Conservation? The Histological Case Studies of Tilos and Kerassia

The present study concerns the histological description of fossilized mammalian bone behavior, under the effect of hydrogen peroxide, acetic acid, and formic acid. These reagents have been applied on such material for decades, mainly for matrix removal and surface cleaning. The material used includes fossil bone parts from two different fossiliferous sites in Greece, Charkadio Cave on Tilos Island (Dodecanese) and Kerassia (Euboea Island). In order to conclude on the extent of histological damage on fossilized bone by the different chemicals and discuss their optimum application on bone, numerous experiments were realized. In each of these, samples from both sites were exposed to different combinations of parameters such as the type and concentration of reagents and the duration of exposure. The methodology applied included the detailed observation of bone histology under a scanning electron microscope (SEM), as well as qualitative chemical analyses through X-ray microanalysis (EDS) and mineralogical analyses by X-ray diffraction (XRD) when needed. pH measurements were collected during each subsequent stage of the experiment. All samples underwent density and porosity measurements before and after treatment. In conclusion, the results of this study confirmed that the initial state of preservation is the determinant factor when deciding upon the conservation strategy to be followed and the type and concentration of the applied chemical on fossilized skeletal remains. Also, it became evident that high concentrations of acetic and formic acid tend to deteriorate the microstructure of fossils and thus render any histological study impossible.