Request permission to export field material for isotopic and diagenesis analysis (Destructive analysis)

Project title
Palaeoenvironment and fossilization at Brad Pit A (Bolt’s Farm karstic system).
Anticipated completion date
We request to export some small-sized fragments of teeth of different taxon (represent here the samples for this study) excavated from the locus BPA (Brad Pit A) of the Bolt’s Farm Karstic System (Klinkert’s). The samples were selected during the excavation (see Sampling Protocol and Justification section). The samples would be exported either at the end of October 2024 or in mid-June 2024 (depending on SAHRA export approval and Ditsong: National Museum of Natural History permission). The diagenesis and isotope analysis may begin shortly after the export and conclude by the end of 2024 (or, if required, the beginning of 2025).
Purpose and scientific merit of the research
The fossil samples exported on a permanent basis from South Africa to conduct Scientific Research which concerns destructive analysis to understand diagenetic transformation of teeth from South African karstic environments.
The chemical and stable isotope compositions of fossil remains of vertebrates provide unique palaeoenvironmental information about the vegetation found in the past ecosystems, the diet and ecology of the fauna, and past climatic variations. However, the reliability of these reconstructions depends on the preservation of the biogenic geochemical record during fossilization processes.
The aim of this project is to determine the preservation level of fossil bone and tooth remains from both the Middle Pliocene Brad Pit A (BPA) locus at Bolt’s Farm Karstic System (Cradle of Humankind, South Africa), and to link the crystal-chemical transformations measured at the molecular scale in fossil apatites to the local physico-chemical conditions prevailing in this fossilization environment.
Some earlier works led to the development of a robust quantification method of the recrystallisation of biological apatite into secondary apatite during fossilisation, relying on attenuated total reflectance infrared (ATR-FTIR) spectroscopy, and demonstrated the capability of fossil bones to record the chemical composition of percolating fluids in the fossilization environment (Aufort et al., 2019). This approach was successfully applied to study the transformation of fossil bones in two distinct cases, the karstic environments of Bolt’s Farm Karstic System (Cradle of Humankind, South Africa), but not at Brad Pit A, and the fluvio-lacustrine environments of the Tugen Hills (Gregory Rift, Kenya) (Aufort et al., 2019). All fossil bone samples exhibited systematic recrystallisation of the original bioapatite into secondary fluorapatite but to various degrees. While the Kenyan samples all showed significant recrystallisation into fluorapatite exclusively, the less fluorinated fossil bones from Bolt’s Farm Karstic System surprisingly also showed transformation into secondary hydroxyapatite, likely linked to higher presence and/or circulation of water.
The project will include the investigation of diagenetic transformation in fossil teeth, which had not been considered in the previous karst studies of Bolt’s Farm Karstic System.
The (destructive) analysis will be carried out by Julie Aufort (IMPMC-Institut de Minéralogie de Physique des Matériaux et de Cosmochimie/Sorbonne Université at Paris) and Loïc Ségalen (M2C-Laboratoire de morphodynamique continentale et côtière/ Université de Rouen Normandie) under the supervision of D. Gommery (CR2P). They require the sampling of about a hundred milligrams of bone or enamel powder and will be performed at IMPMC within the lab’s spectroscopy platform that possesses the adequate equipment (ATR-FTIR spectrometer with diamond and germanium ATR crystals).
In parallel to the characterization of the state of preservation of the samples, stable isotopes analyses (δ13C and δ18O) will be performed on the tooth enamel in order to understand the climate and the environment evolution. The measurements of stable light isotopes ratios (δ18O and δ13C) on extinct mammals have been largely explored to provide valuable information about their diet habits and to assess the environments and the climate they lived under (Roche et al., 2013). The carbon isotope will help us to define the type of plants present in the ecosystem (C4 or C4 plants), and if the animals evolved in a close or open environment. In the case of oxygen, the isotopic composition of enamel depends on climatic factors (which affect the water in the environment, and thus the precipitations) and the filters related to the behaviour of the animal. For example, elevated values of δ18O indicate an origin of water ingested by an animal derived from the plants eaten rather than from free water and equally, of conditions of low humidity in the environment (Levin et al., 2008).
The isotopic analyses will be realized with a mass spectrometer at Sorbonne University. 10mg of enamel powder are needed to perform the analyses.
Sampling Protocol and Justification
The samples were chosen during the excavation at Brad Pit A (BPA) in order to avoid using some specimen with a high level of interest in palaeontological study (morphology, phylogeny, biological adaptability) (as previously mentioned). In order to avoid receiving a traditional collection number for the Bolt's Farm collection, which is curated in the Plio-Pleistocene Palaeontology division, they have been given a specific catalogue number for isotopic and diagenesis analysis (with the BPA.ISO prefix). This keeps the fossil collection from having a gap (the analysis done here is destructive). The samples range in length from half a centimeter to around four centimeters, and they are very fragmented. Only the general zoological group (Rhinocerotidae, Bovidae, and Cercopithecoidea) may be recognized; they are not useful for museography or for a more in-depth palaeontological investigation.
The behavior of the three zoological groups—Rhinocerotidae, Bovidae, and Cercopithecoidea—represented by the current samples varies, which can aid in our knowledge of past habitats. To fully comprehend the inherent variety in each zoological group, it is crucial to have multiple samples.
Understanding the diagenesis process, which may potentially be changeable, is equally crucial.Evidence of the researcher’s competence and funding
D. Gommery, L. Kgasi and N. Vilakazi are the 3 co-permit holders for the excavation permit delivered by SAHRA. They are recognized for their scientific contributions concerning Bolt’s Farm Karstic System (D. Gommery and N. Vilakazi received the Price ‘Tremplin pour l’Avenir’ from the French Academy of Science). Several funding sources, including the French Ministry of Foreign Affairs, the University of Johannesburg, the NRF, the French Academy of Science, the CNRS, and Fondation Ars Cuttoli (via Fondation de France), have contributed to the fieldwork project.
J. Aufort is an expert in diagenesis and has created a novel method for analyzing the fossilization process (Aufort et al., 2019a,b). Isotope analysis expert L. Ségalen specializes in Southern and East Africa (Ségalen et al., 2007; Roche et al., 2013). The Sorbonne University has a robust spectroscopic platform with the necessary tools (ATR-FTIR spectrometer with germanium and diamond ATR crystals). The Sorbonne University will cover the expense of the analyses through the IMPMC-Institut de Minéralogie de Physique des Matériaux et de Cosmochimie's funding.Justification for use of museum specimens
These samples are not curated with the overall fossil collection; instead, they have a unique research catalogue number. Material excavated at Brad Pit A in relation to the permit provided by SAHRA is officially curated at the Ditsong: National Museum of Natural History. These samples for isotope and diagenesis require consent from the Ditsong: National Museum of Natural History in order to be exported (with a SAHRA export permit). Since the locus BPA was found in 2010, the Ditsong: National Museum of Natural History has been the repository for all fossil material excavated within its boundaries. BPA produced a significant fossil collection that is noteworthy for its scientific value in addition to its quantity. The scientific community's understanding of the Plio-Pleistocene environmental change and human evolution will benefit from this work, which will also strengthen the DNMNH.
Assurance that the results of the study will be published in a peer-reviewed journal
The Bolt's Farm team routinely publishes the findings from their research on the many loci within the Bolt's Farm Karstic system in peer-reviewed journals. Their most recent two publications are Gommery et al. (2023) and Senut et al. (2022). The anticipated findings from these isotopic and diagenesis analyses will be published in a synthetic paper that focuses on the BPA geology. Some findings about the diagenesis process and the evolution of ecosystems in Southern and East Africa during the Neogene and Quaternary will be published in other publications. These articles will also compare these two African countries.
References:
Aufort J., Gommery D., Gervais C., Ségalen L., Labourdette N., Coehlio-Diogo C. & Balan E. (2019a) Assessing bone transformation in late Miocene and Plio-Pleistocene deposits of Kenya and South Africa. Archaeometry 65, 5, 1129-1143.
https://doi.org/10.111/arcm.12471
Aufort J., Gervais C., Ségalen L., Labourdette N., Coehlio-Diogo C., Baptistea B., Beyssaca O., Amiot R., Lécuyer C. & Balan E. (2019b) Atomic scale transformation of bone in controlled aqueous alteration experiments. Palaeogeography Palaeoclimatology Palaeoecology 526, 80-95. https://doi.org/10.1016/j.palaeo.2019.03.042
Gommery D., Kgasi L., Vilakazi N., Sénégas F., Pickford M., Kuhn B., Schnyder J. & Pois V. (2023). First in situ middle Pliocene cercopithecoid fossils from the Palaeokarst System of Bolt’s Farm (South Africa). Geodiversitas 45, 5, 163-195.
https://doi.org/10.5252/geodiversitas2023v45a5
Levin N.E., Cerling T.E., Passev B.H., Harris J.M. & Ehleringer J.R. et al. (2008). A stable isotope aridity index for terrestrial environments. PNAS 103, 11201-11205.
https://doi.org/10.1073/pnas.0604719103
Roche D., Ségalen L., Senut B. Pickford M. (2013). Stable isotope analyses of tooth enamel carbonate of large herbivores from the Tugen Hills deposits: environmental context of the earliest Kenyan hominids. Earth Planetary Science Letters 381, 39-51.
https://doi.org/10.1016/j.epsl.2013.08.021
Ségalen L., Lee-Thorp J.A., Thure Cerling 4(2007). Timing of C 4 grass expansion across sub-Saharan Africa. Journal of Human Evolution 53 (2007) 529-559
https://doi.org/10.1016/j.jhevol.2006.12.010
Senut B., Sénégas F., Gommery D., Vilakazi N., Kgasi L. & Pickford M. (2022). New specimen of Mylomygale (Macroscelidea, Macroscelididae) from the Pliocene of South Africa. Journal of African Earth Sciences.
https://doi.org/10.1016/j.jafrearsci.2022.104668