Paleoenvironmental interpretations of Irati and Mangrullo Formations (Permian of Paraná Basin) based on rocks and fossil bones through spectroscopy techniques

Abstract

The hydroxyapatite of fossil bones can provide paleoenvironmental information, because throughout the fossil-diagenetic process, the fossils can incorporate elements from the sedimentary rocks that involved them. In this way, the present study aimed for geochemical patterns in mesosaurid bones and their respective host rocks to project the paleoenvironmental conditions at deposition/diagenesis’ time. For this purpose, Raman Spectroscopy and X-Ray Fluorescence analysis were performed. The samples came from Irati (S1 – São Matues do Sul, S2 – Assistência, S4 – Aceguá e S5 – São Gabriel) and Mangrullo (S3 – Uruguay) Formations. We found similar geochemical composition between S1 and S5; S3 and S4 which also indicates a similar paleoenvironmental context. The samples S1 and S5 have relatively high Al, Si and Sr contents which can represent acidic conditions and high depths. The second set (S3 and S4) have similar contents of Al, Si and Ca, but it is worth to note that the Si and Ca contents are slightly different. The Si and Ca contents suggest that S3 was slightly deeper and less acidic when compared to S4. In general, the first set (S1 and S5) were deeper and more acidic than the second (S3 and S4). The S2 sample is out of line with the others, corresponding to shallow or coastal and more basic paleoenvironment. Overall, our results agree with previous studies about the past environment where mesosaurs lived. Also, shows that spectroscopy techniques are reliable and should be used to refine paleoenvironmental interpretations.