Diagenetic processes in the fossilized carapace of Neosclerocalyptus sp. from the Paraguayan Chaco

Abstract

Paleometry is essential in analyzing fossil remains, revealing diagenetic processes through physicochemical characterization techniques that identify crystalline and chemical structures, as well as elemental composition and changes observed via electron microscopy. This study examines the fossilized carapace of Neosclerocalyptus sp. from the Paraguayan Chaco, employing these methodologies to understand its diagenetic transformation. Fourier transform infrared (FT-IR) spectra identified phosphate, carbonate, and amide I and II groups. The Gaussian deconvolution model applied to the FT-IR spectra distinguished individual bands within overlapping vibrational modes, providing insights into the presence of stoichiometric and non-stoichiometric calcium phosphates. X-ray diffraction patterns confirmed the crystallinity and apatite nature of the sample, while energy dispersive X-ray fluorescence and scanning electron microscopy energy-dispersive spectroscopy assessed its elemental composition and microstructural characteristics. The results indicated the inclusion of new crystalline phases (quartz) and changes in mineralogy and crystallinity due to environmental interactions. A diagenetic pathway model is proposed, involving initial development, exposure to calcium carbonate-rich water, hydroxyapatite recrystallization, calcite infiltration in pores, and incorporation of new elements. This study enhances the understanding of fossil preservation and environmental influences on diagenetic processes at a regional level as well as being one of the first works on glyptodont carapace characterizations in South America.