Search Results (21)

Understanding the composition and diagenetic processes of the deposition environment is pivotal to understanding why bone undergoes preservation or diagenesis. This research explores the complex nexus of diagenesis at the extremes of preservation, via the interdependent chemical, and short- and long-term microbial processes that influence diagenesis. These processes include dissolution, ion exchange, hydrolysis, recrystallisation, waterlogging, acidity and alkalinity, soil composition, redox potential, bacterial activity, and microbiome composition. Diagenetic processes are discussed in relation to typical sites and sites with extremes of preservation. Understanding site conditions that impact diagenetic processes is critical to understanding the visual features presented in recovered skeletal material, ensuring an appropriate post-mortem interval is assigned, and for subsequent post hoc analysis of bone. Full article

Because fossilized skeletal remains and enclosing sedimentary rocks experience similar diagenetic conditions (i.e., temperature, pressure, and pore fluid interaction,) enclosing sedimentary rocks may provide insight into bone diagenesis. A fossil assemblage, including in situ dinosaur fossils, was discovered in Makoshika State Park near Glendive, MT. Fossil-bearing sandstone is a crevasse splay deposit, and fossils show no sorting or preferred orientation. Bone-bearing sandstone exhibits evidence for intense diagenesis, suggesting a maximum temperature of ~90 °C. Concretion associated with fossils includes two distinctive matrices: dark- and light-colored matrices. Another concretion was found in channel sandstone near the base of the outcrop. These carbonate phases have distinctive isotopic compositions; δ¹³C values for dark-colored matrices, light-colored matrices, and spheroidal concretion are −7.5, 2.1, and −22.4‰ (VPDB), respectively, and their δ¹⁸O values are 16.4, 25.9, and 17.8‰ (VSMOW), respectively. In contrast, fossilized bone δ¹³C and δ¹⁸O values were −4.4‰ (VPDB) and 20.6‰ (VSMOW), respectively, suggesting fractionation with pore fluid was limited. Early carbonate precipitation evidenced by grain coating may have reduced interaction between pore fluids and fossils. Although concretion formation and permineralization do not appear to directly aid in fossil preservation, concretions preserve valuable evidence for diagenetic history. Full article

Archaeological bone chemical composition is modified post-mortem by diagenesis processes, and over decades, several authors have proposed different protocols to avoid post-depositional contamination that can carry to misleading interpretations about the lifestyle and origin of ancient populations. In this work, a methodological approach based on rare earth elements analysis was developed to determine diagenetic alterations on femurs, humeri, and skull surfaces, and internal layers from thirteen individuals exhumed during fieldwork in the Fatih Sultan Mehmet Mosque at Rozafa Castle (Shkodër, Albania). Major, minor, and trace elements, including rare earth elements, were measured employing spectrometric techniques, and the obtained data were statistically processed by principal component analysis and one-way ANOVA to select the best preserved bones. The results show that in general, the internal parts of bones, especially skulls, suffered post-depositional chemical contamination. Finally, to show the effectiveness of the proposed approach, a diet reconstruction employing log(Sr/Ca) and Zn/Ca was tested, obtaining results that are in line with the literature describing a diet based on a mixed economy, mostly agricultural products with low protein intakes. Full article

The petrous bone generally preserves ancient DNA better than other fossil bones. One reason for this is that the inner layer of the petrous bone of pigs and humans contains about three times as many osteocytes as other bones, and hence more DNA. A FIB-SEM study of modern pig petrous bones showed that the 3D structure of the thin inner layer is typical of woven bone that forms in the fetus, whereas the thicker outer layer has a lamellar structure. The lamellar structure is common in mammalian bones. Here we study human petrous bones that are about 2500 years old, obtained from three Phoenician sites in Sicily, Italy. A detailed FIB-SEM study of two of these bones, one well preserved and the other poorly preserved, shows that the 3D bone type structure of the human petrous inner layer is woven bone, and the outer layer is lamellar bone. These are the same bone type structures found in pig petrous bones. Furthermore, by comparing nine differently preserved petrous bones from the same archaeological region and age, we show that their collagen contents vary widely, implying that organic material can be significantly altered during diagenesis. The mineral crystals are better preserved and hence less crystalline in the inner layers compared to the outer layers. We therefore infer that the best-preserved DNA in fossil petrous bones should be found in the thin inner layers immediately adjacent to the otic cavity where much more DNA is initially present and the mineral phase tends to be better preserved. Full article

A fossil mysticete was discovered along the southwestern coast of Spain, occurring in a block detached from the Neogene deposits exposed along a coastal cliff at the locality of Conil de la Frontera (Cádiz, Spain). These deposits range from Pliocene to Pleistocene in age and include shallow-marine, mixed carbonate–siliciclastic sediments, with the whale being found in occurrence of a stratigraphic unconformity marked by Thalassinoides burrows. ⁸⁷Sr/⁸⁶Sr analyses on oyster shells associated with the skeleton suggest an Early Pliocene age, in agreement with the age of the lowermost unit cropping out at the study site. The studied cetacean specimen consists of an articulated, almost complete balaenopteroid skeleton exposed in the field dorsal side up; being contained in an upside-down block, however, it is preserved in ventral disposition. Bones exhibit a low degree of preservation of the cortical bone tissue, which locally features shark bite marks and Osedax traces as well as abundant encrustations of barnacles and ostreids. Two shark teeth were also found near the skeleton. Bones have preserved their main histological features, even though they locally exhibit microcracks, dissolution, substitution by Fe oxides, and microborings. Sediment particles and late diagenetic cements fill the medullary cavities. We propose that the whale carcass experienced refloating before sinking to the seafloor and that the skeleton was probably exposed on the seafloor for some time before being eventually buried. Full article

Microscopic analysis of fossils from the Lightning Ridge district of northwestern New South Wales, Australia, shows that opal has been typically deposited in variable cavities left by the degradation of the original organic material. Fine-grained, clay-rich sediments have preserved the external morphology, and opalization has produced detailed casts with different modes of preservation of internal details. Plant remains include cones, cone scales, fruiting bodies, and seeds, but the most common specimens are twigs, stems, and wood fragments. These specimens commonly contain angular inclusions that represent small tissue fragments produced by the degradation of the original wood. Inclusions commonly have a “hollow box” structure where the organic material has decomposed after the initial opal filling of the mold. These spaces commonly contain traces of the cellular architecture, in the form of wood fiber textures imprinted on the cavity wall, degraded cellular material, and silicified tracheids. Opal casts of mollusk shells and crustacean bioliths preserve the shape but no calcium carbonate residue. Likewise, opal casts of vertebrate remains (bones, teeth, osteoderms) lack preservation of the original bioapatite. These compositions are evidence that burial in fine clays and silts, isolated from the effects of water and oxygen, caused protracted delays between the timing of burial, decomposition, and the development of vacuities in the claystones that became sites for opal precipitation. The length of time required for the dissolution of cellulosic/ligninitic plant remains, calcium carbonate items, and calcium phosphates in bones and teeth cannot be quantified, but evidence from opal-bearing formations worldwide reveals that these processes can be very slow. The timing of opalization can be inferred from previous studies that concluded that Cenozoic tectonism produced faults and fissures that allowed horizontal and lateral movement of silica-bearing groundwater. Comparisons of Australian opal-AG with opal from international localities suggest that opalization was a Neogene phenomenon. The transformation of Opal-AG → Opal-CT is well-documented for the diagenesis of siliceous biogenic sediments and siliceous sinter from geothermal areas. Likewise, precious and common opal from the late Miocene Virgin Valley Formation in northern Nevada, USA, shows the rapidity of the Opal-AG → Opal-CT transformation. Taken together, we consider this evidence to indicate a Neogene age for Lightning Ridge opalization and by inference for the opalization of the extensive opal deposits of the Great Artesian Basin in Australia. New paleontology discoveries include a surprising level of cellular detail in plant fossils, the preservation of individual tracheids as opal casts, evidence of opalized plant pith or vascular tissue (non-gymnosperm), and the first report of Early Cretaceous coprolites from New South Wales, Australia. Full article

Recent experiments have heightened our understanding of reactions which can stabilize biomolecules during early diagenesis, yet little remains known about how groundwater chemistry can aid or hinder molecular preservation within a bone through geologic time. To elucidate this issue, we conducted actualistic experiments of bone decay employing varied fluid compositions to simulate a suite of groundwaters. Modern domestic chicken (Gallus gallus) femora were placed in a matrix of compositionally- and texturally-mature, fluvially-deposited sand. To simulate groundwater flow, deionized water or solutions enriched in calcium carbonate, phosphate, or iron were percolated through separate trials for a period of 90 days. After completion of the experiment, degradation of the bones was examined via histologic thin sectioning and two immunoassays against collagen I, the primary bone structural protein: immunofluorescence and enzyme-linked immunosorbent assay. Collagen loss was found to be greatest in the iron trial and least in the calcium carbonate trial, the latter of which experienced partial permineralization with calcite over the course of the experiment. Specifically, the iron trial was found to retain only ~35 ng of collagen I per 100 ng of protein extract, whereas the calcium carbonate trial retained ~90 ng of collagen I. Further, in the iron and calcium carbonate trials, cementation of sediment onto bone surfaces preferentially occurred over more porous regions of the epiphyses, perhaps stimulated by greater release of decay compounds from these regions of the bones. Of the two trials exhibiting intermediate results, the phosphate trial induced slightly greater decay of collagen than the deionized water control, which retained ~60 ng and ~80 ng of collagen I per 100 ng of protein extract, respectively. These results demonstrate that highly acidic conditions during early diagenesis can overwhelm any preservative effects of free radical-mediated stabilization reactions, whereas early-diagenetic permineralization can drastically slow biomolecular decay (ostensibly by hampering microbial access to the interior of a bone), thereby increasing the likelihood of a bone to retain biomolecules and/or their decay products through protracted diagenesis. Future variations of this actualistic experiment employing varied durations, solute concentrations, bacterial communities, pH values, and/or host sediments could provide further important insights into the ways in which early-diagenetic environments control the initial decay of biomolecules within bone and other tissues. Full article

It is well understood that intrinsic factors of bone contribute to bone diagenesis, including bone porosity, crystallinity, and the ratio of organic to mineral components. However, histological analyses have largely been limited to adult bones, although with some exceptions. Considering that many of these properties are different between juvenile and adult bone, the purpose of this study is to investigate if these differences may result in increased degradation observed histologically in fetal and juvenile bone. Thirty-two fetal (n = 16) and juvenile (n = 16) Sus scrofa domesticus femora subject to different depositions over a period of two years were sectioned for histological observation. Degradation was scored using an adapted tunneling index. Results showed degradation related to microbial activity in both fetal and juvenile remains across depositions as early as three months. Buried juvenile remains consistently showed the greatest degradation over time, while the blanket fetal remains showed more minimal degradation. This is likely related to the buried remains’ greater contact with surrounding soil and groundwater during deposition. Further, most of the degradation was seen in the subendosteal region, followed by the subperiosteal region, which may suggest the initial microbial attack is from endogenous sources. Full article

Human skeletons associated with early gold mining in Johannesburg, South Africa are investigated. An unmarked cemetery was buried beneath a mine dump which resulted in macroscopically stained and poorly preserved bones. Histological assessments were conducted to understand the postmortem treatment of the remains, determine the extent of bone degradation, and understand how this environment affected the bone’s microstructure. Various diagenetic alterations and the general histological index were assessed using normal and polarized light microscopy of thin anterior midshaft femur sections (n = 50). Degradation was identified in the periosteal and endosteal regions, while the intra-cortical region remained well-preserved. Bacterial bioerosion, microcracks, infiltrations, inclusions, and staining were found throughout the sample. Numerous non-Wedl micro-foci of destruction were observed, filled with exogenous material. The degradation suggested that the remains were buried in neutral soil that was subsequently covered by acidic mine dumps which resulted in a corrosive environment. Although the skeletons were poorly preserved, their histological integrity was more promising, especially the intra-cortical area. This is important for future investigations of archaeological bone, as this area can lead to more accurate descriptions of skeletal assemblages. Targeted sampling of this region could produce promising estimates of age, descriptions of pathology, and biomolecular results, which require further study. Full article

Bones offer a great amount of information on ancient populations regarding both their lifestyle habits and the influence of the living area. Bones are composed by an inorganic component, i.e., carbonated hydroxyapatite (Ca₁₀[(PO₄)₆−x(CO₃)_x](OH)₂), and an organic matrix (mainly proteins and collagen). After death, bones are subjected to diagenetic processes, with changes in structure, morphology, and chemical composition. All these modifications strictly depend on several factors, including the nearby environment, the climate, and the burial modality. Hence, a precise knowledge of the diagenetic processes affecting bones after death is mandatory. In this study, archeological human bones from the Garamantian necropolis of Fewet (Libyan Sahara) were analyzed by ATR–FTIR spectroscopy to elucidate the role of the burial location and modality, as well as the highly arid environment in the diagenesis rate. Several spectral parameters related to structural and chemical features of the organic and mineral components (i.e., AmideI/PO₄, C/P, MM, FWHM₆₀₃, and IRSF indexes) were statistically analyzed. Spectral data were compared with those from modern ruminants from the same site to evaluate a possible time-dependent correlation between the chemical composition and the diagenetic processes. A mild diagenesis was found in all human bones, even though it had a variable degree depending on the burial location. Full article

Elephants are currently the largest terrestrial mammals, along with their extinct ancestor the mammoth. These species are of great interest due to their geographic distribution and ecological importance. However, the bone mineral characteristics of their skeleton as well as their alteration during burial processes over millions of years have been poorly investigated. In the current research, we analyzed the compositional and structural mineral properties of different types (i.e., long and flat bones) of elephant and mammoth bones. For this purpose, we performed a comparative study between these bone types using complementary analytical techniques based on X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, and inductively coupled plasma spectroscopic analysis. The chemical composition of the samples shows a relative loss of a considerable percentage of water and organic matter components for the fossilized bone, accompanied by a higher bone mineralization degree and the presence of other crystalline phases (i.e., calcite and pyrite) related to a certain degree of diagenesis alteration. Our results also show a variation in the crystalline properties of mammoth bone related to the recrystallization process during the dissolution–precipitation transformation through diagenetic burial. This research provides relevant information for understanding the mineral properties of different types of bones and their possible changes during diagenesis. Full article

After death, diagenesis takes place. Numerous processes occur concomitantly, which makes it difficult to identify the diagenetic processes. The diagenetic processes refer to all processes (chemical or physical) that modify the skeletal remains. These processes are highly variable depending on the environmental factors (weather, temperature, age, sex, etc.), especially in the early stages. Numerous studies have evaluated bone diagenetic processes over long timescales (~millions of years), but fewer have been done over short timescales (between days and thousands of years). The objective of the study is to assess the early stages of diagenetic processes by Raman microspectroscopy over 12 months. The mineral and organic matrix modifications are monitored through physicochemical parameters. Ribs from six humans were buried in soil. The modifications of bone composition were followed by Raman spectroscopy each month. The decrease in the mineral/organic ratio and carbonate type-B content and the increase in crystallinity reveal that minerals undergo dissolution–recrystallization. The decrease in collagen cross-linking indicates that collagen hydrolysis induces the fragmentation of collagen fibres over 12 months. Full article

Raman micro-spectroscopy is a non-destructive and non-contact analytical technique that combines microscopy and spectroscopy, thus providing a potential for non-invasive and in situ molecular identification, even over heterogeneous and rare samples such as fossilized tissues. Recently, chemical imaging techniques have become an increasingly popular tool for characterizing trace elements, isotopic information, and organic markers in fossils. Raman spectroscopy also shows a growing potential in understanding bone microstructure, chemical composition, and mineral assemblance affected by diagenetic processes. In our lab, we have investigated a wide range of different fossil tissues, mainly of Mesozoic vertebrates (from Jurassic through Cretaceous). Besides standard spectra of sedimentary rocks, including pigment contamination, our Raman spectra also exhibit interesting spectral features in the 1200–1800 cm⁻¹ spectral range, where Raman bands of proteins, nucleic acids, and other organic molecules can be identified. In the present study, we discuss both a possible origin of the observed bands of ancient organic residues and difficulties with definition of the specific spectral markers in fossilized soft and hard tissues. Full article

Recent recoveries of peptide sequences from two Cretaceous dinosaur bones require paleontologists to rethink traditional notions about how fossilization occurs. As part of this shifting paradigm, several research groups have recently begun attempting to characterize biomolecular decay and stabilization pathways in diverse paleoenvironmental and diagenetic settings. To advance these efforts, we assessed the taphonomic and geochemical history of Brachylophosaurus canadensis specimen MOR 2598, the left femur of which was previously found to retain endogenous cells, tissues, and structural proteins. Combined stratigraphic and trace element data show that after brief fluvial transport, this articulated hind limb was buried in a sandy, likely-brackish, estuarine channel. During early diagenesis, percolating groundwaters stagnated within the bones, forming reducing internal microenvironments. Recent exposure and weathering also caused the surficial leaching of trace elements from the specimen. Despite these shifting redox regimes, proteins within the bones were able to survive through diagenesis, attesting to their remarkable resiliency over geologic time. Synthesizing our findings with other recent studies reveals that oxidizing conditions in the initial ~48 h postmortem likely promote molecular stabilization reactions and that the retention of early-diagenetic trace element signatures may be a useful proxy for molecular recovery potential. Full article

The new exposure of the Upper Muschelkalk clays and dolomites located south of Kalety (Tarnogórski District, Silesia, Poland) provided numerous remains of vertebrates represented by teeth, scales, long bones, and coprolites. Despite the influence of hydrothermal processes leading to dolomitization and Zn-Pb deposit formation, the preservation of fossil remains is good. The taxonomic diversity and accumulation of vertebrate debris in the dolomite are similar to other “bone beds” from the Muschelkalk and the Lower Keuper units. The SEM-EDS, EMP-WDS, and XRD analyses confirm that the examined remains consist of hydroxylapatite containing carbonate ions. Most vertebrate teeth as well as some bone fragments show zoning in the BSE imaging. In tooth cross-sections, three or two zones are preserved: (I) the outermost zone, associated with diagenetic mineralization of enameloid apatite, (II) a intermediate zone (orthodentine), and (III) the most porous internal zone (osteodentine). Decreasing P, Ca, Sr in the composition of the apatite which forms successive zones, is visible from the most external to the central part. Selective diagenetic substitution and adsorption of some elements by apatite crystals can allow recognition of the genetic origin of highly damaged or transported fragments scattered in the sedimentary layers. The chemical behavior of bioapatite, from deposition to digenesis, shows its useful role for identification of the formation process and potential, younger changes (e.g., hydrothermal overprint). The X-ray diffraction data, particularly cell parameters “a” and “c”, can determine the degree of crystallinity and/or diagenesis. Moreover, correlation between some elements/ions (e.g., Sr, Ba, Ca, Mg, F, OH) can be helpful for the identification of the fossil type, especially if the bones are small and incomplete. Full article