Assessing bone transformation in late Miocene and Plio‐Pleistocene deposits of Kenya and South Africa

Abstract

Bone reactivity offers a potential way to record local physical–chemical conditions prevailing in fossilization environments and archaeological sites. In the present study, a series of fossil bone samples from the karstic environments of the Bolt's Farm cave system (Cradle of Humankind, South Africa) and from fluvio‐lacustrine environments of the Tugen Hills (Gregory Rift, Kenya) is analysed. The chemical composition and infrared and nuclear magnetic resonance (NMR) spectroscopic properties of fossil samples point to a transformation of the biogenic apatite and formation of secondary apatite. Depending on the sample, the secondary apatite corresponds to a carbonate‐bearing hydroxy‐ or fluor‐apatite. The maximum fraction of secondary apatite is close to 60%, coinciding with previous observations in experimental alteration of bone in aqueous solutions and suggesting that a fraction of pristine biological apatite is likely to be preserved. The present results also suggest that the acetic acid treatment of fossil samples moderately increases their average crystallinity but may dissolve carbonate‐rich domains of secondary apatite.

Atomic scale transformation of bone in controlled aqueous alteration experiments

“…related to electrostatic interactions between apatite particles and therefore depending on porosity, grain size and shapes of particles. In contrast, the position and line shape of weaker and narrower bands, such as the ν 1 PO 4 band, are less affected by these electrostatic effects and are thus expected to provide a better insight into the short-range order of the crystal structure (Balan et al, 2011;Aufort et al, 2016Aufort et al, , 2018Aufort et al, , 2019. However, the overlap of the ν 1 PO 4 band with the stronger ν3 PO4 band in the diamond ATR spectrum significantly affects the line shape of the ν 1 PO 4 band.…”

Internalization of Fluoride in Hydroxyapatite Nanoparticles

“…Geologists have often used ″mineral replacement″; 37 elsewhere, the term ″transformation″ is used. 38,39 We opted to use ″internal-ization″ because it differentiates from adsorption phenomena, whereas the other terms have not. Critical time scales in water treatment are typically much shorter than geological apatite replacement 37 and/or bone transformations.…”

“…Critical time scales in water treatment are typically much shorter than geological apatite replacement 37 and/or bone transformations. 38,39 Hence, it is necessary to concern ourselves with adsorption apart from internalization because they are likely both mechanistically and kinetically distinct. Moreover, the higher bulk versus adsorption F − capacity in HAP NPs presents the greatest opportunity to significantly improve uptake performance.…”

Experimental Aqueous Alteration of Cortical Bone Microarchitecture Analyzed by Quantitative Micro-Computed Tomography

“…Bones are porous materials, characterized by the presence of large contact surfaces for interaction with water, which was shown to play an important role during early diagenesis Hedges, 2002;Aufort et al, 2019). Although bone itself is highly insoluble in neutral water (Horvath, 2006), aqueous fluids can lead to degradation or preservation of mineralized tissues under certain conditions, especially during the early stages of diagenetic alteration.…”

“…However, an advantage of CT techniques is their non-destructive approach, which allows studying rare or otherwise valuable samples. In addition, CT permits systematic and comparative studies on bone taphonomy before and after experiments, which so far for methodological reasons were based on limited structural and chemical investigations of experimentally altered samples (Blake et al, 1997;Blake et al, 1998;Zazzo et al, 2004;Schwermann et al, 2012;Kohn and Moses, 2013;Keenan and Engel, 2017;Aufort et al, 2019;Caruso et al, 2020;Gäb et al, 2020).…”