Interface Focus

Graptolites are fossils from the mid-Cambrian to lower Carboniferous periods that inform both our understanding of evolution and the exploration of shale gas [1-4]. The identification of graptolite species remains a visual task carried out by experienced taxonomists because their fine-grained morphologies and incomplete preservation in multi-fossil samples have hindered automation. Artificial intelligence (AI) holds great promise for transforming such meticulous tasks, and has already proven useful in applications ranging from animal classification to medical diagnostics [5-15]. Here we demonstrate that graptolites can be identified with taxonomist accuracy using a deep learning model [16-18]. We develop a convolutional neural network to classify macrofossils, and construct a comprehensive dataset of >34,000 images of 113 graptolite species annotated at pixel-level resolution to train the model. We validate the models performance by comparing its ability to identify 100 images of graptolite species that are significant for rock dating and shale gas exploration with 21 experienced taxonomists from research institutes and the shale gas industry. Our model achieves 86% and 81% accuracy when identifying the genus and species of graptolites, respectively; outperforming taxonomists in terms of accuracy, time, and generalization. By investigating the decisions made by the neural network, we further show that it can recognise fine-grained morphological details better than taxonomists. Our AI approach, providing taxonomist-level graptolite identification, can be deployed on web and mobile apps to extend graptolite identification beyond research institutes and improve the efficiency of shale gas exploration.

Raman spectroscopy has facilitated rapid progress in the understanding of patterns and processes associated with biomolecule fossilization and revealed the preservation of biological and geological signatures in fossil organic matter. Nonetheless six large-scale statistical studies of Raman spectra of carbonaceous fossils, selected from a number of independent assessments producing similar trends, have been disputed. Alleon et al. (21) applied a wavelet transform analysis in an unconventional way to identify frequency components contributing to two baselined spectra selected from these studies and claimed similarities with a downloaded edge filter transmission spectrum. On the basis of indirect comparisons and qualitative observations they argued that all spectral features detected, including significant mineral peaks, can be equated to edge filter ripples and are therefore artefactual. Alleon et al. (21) extrapolated this conclusion to dispute not only the validity of n>200 spectra in the studies in question, but also the utility of Raman spectroscopy, a well established method, for analysing organic materials in general. Here we test the claims by Alleon et al. (21) using direct spectral comparisons and statistical analyses. We present multiple independent lines of evidence that demonstrate the original, biologically and geologically informative nature of the Raman spectra in question. We demonstrate that the methodological approach introduced by Alleon et al. (21) is unsuitable for assessing the quality of spectra and identifying noise within them. Statistical analyses of large Raman spectral data sets provide a powerful tool in the search for compositional patterns in biomaterials and yield invaluable insights into the history of life.

Recovering well-preserved vertebrate remains from underwater caves has provided critical insights into archaeological and palaeontological records worldwide. However, understanding how bone assemblages form and are modified in underwater environments remains limited due to stable low energy burial conditions that produce time-averaged deposits, and underwater settings that hinder traditional recording and recovery methods. This study applies an actualistic taphonomic framework to three assemblages of domesticate animal bones (N = 231) from two underwater caves, Green Waterhole and Gouldens Sinkhole, near Mount Gambier, South Australia, encompassing known submerged (wet; N = 134) and dry (N = 97) burial conditions. The assemblages were examined to assess how wet and dry cave environments impact bone distribution, surface and microstructural modification. Radiocarbon dating of 41 specimens indicates that domesticate fauna were deposited over decadal and centennial timescales, allowing taphonomic signatures to be contextualised through time. Statistically significant differences were identified between wet and dry burial contexts. Bones recovered from wet contexts exhibit mostly better preservation, including skeletal elemental completeness, surface, and microstructure, than those from dry caves. However, some of the submerged specimens also have elevated frequencies of bone surface corrosion with macroscopic evidence for heterogenous black biological staining, algal or biofilm attack, and a distinctive form of circular etching. Histotaphonomy further reveals patterns of peripheral cyanobacterial tunnelling across most bones recovered from submerged contexts. Bones from dry environments were dominated by terrestrially linked tunnelling across all regions of the bone cortex. These findings can be explained by variation in light availability across different cave zones which influences biological activity and, in turn, the expression of taphonomic markers on bone externally and at the microstructural level. This is the first study to provide a benchmark bone dataset for reconstructing depositional histories and post-depositional reworking in underwater cave environments under a taphonomic framework.

Trilobites, a diverse clade of Palaeozoic arthropods, repeatedly converged on the trinucleimorph morphology. Trinucleimorphs possessed vaulted cephala with a broad anterior fringe and prominent posteriorly orientated genal prolongations. Various functional hypotheses have been proposed for the fringe, however the possible function of the genal prolongations has received less attention. Here we use a computational fluid dynamics approach to test whether these prolongations served a hydrodynamic function: generating negative lift to allow trinucleimorphs to remain in place on the seafloor and prevent overturning within fast flowing water. We simulated the performance of cephala with broad, narrow, and absent genal prolongations in a benthic environment with flow speeds ranging from 0.05-0.5 m s-1, in two cephalic postures. The first posture had the anterior of the cephalon parallel to the seafloor, while for the second the genal prolongations were parallel to the seafloor. Posture and presence of genal prolongations were found to be important for generating negative lift, with performance improving under faster flow speeds. No significant difference between narrow and broad genal prolongations was detected. This study provides support for genal prolongations serving a hydrodynamic function, similar to the femurs of some insect larvae, however, it does not preclude prolongations also serving additional functions as snowshoes or antipredatory deterrents.

Elucidating the most probable compositions of the first cell membranes prior to the origin of life, within a laboratory setting, requires experiments with organic molecules and chemical conditions representative of those present on the early Earth. As such, the membrane forming molecules used in these experiments are described as prebiotically plausible, i.e., they could have formed through abiotic reactions and be available for membrane formation prior to the emergence of biology. Similarly, the chemical properties of solutions in which these membranes are formed (e.g., pH, temperature, ionic strength) must represent the early Earth environmental conditions under investigation. Here, using a combined confocal and transmission electron microscopy approach, we show that prebiotically plausible organic molecules, in solutions representative of Hadean submarine alkaline hydrothermal vents, form aggregated structures with substantial morphological diversity. The structures hold the potential for use as traces of prebiotic processes in the ancient rock record. In addition, many of the structures are morphologically similar to those which are presented as early microfossils, thus highlighting the limitations of morphological interpretation in these types of studies. Detailed analyses of abiotic organic structures are essential for our understanding of the earliest living organisms on Earth, as well as for our interpretation of any potential biosignatures recovered in the future from extra-terrestrial bodies.

In pediatric acute lymphoblastic leukemia (ALL), central nervous system (CNS) involvement is staged using white blood cell (WBC) counts from lumbar punctures (LPs), microscopy of LP-derived cells, and CNS imaging. CNS staging informs the need for additional intrathecal chemotherapy, which can result in side-effects including significant neurotoxicity. However, nearly 20% of LPs are traumatic, or contaminated by peripheral blood. In these cases, the Steinherz-Bleyer (S-B) algorithm is used instead of WBC counts to determine CNS involvement. The intuition for this algorithm has not been presented. In this work, we conceptualize LP lab values as a mixture of blood and cerebrospinal fluid (CSF) and present this mixture as a convex combination problem. Then, we demonstrate that the S-B algorithm asks whether the CSF to blood WBC ratio is at or above that of the mixing ratio (i.e., contaminated to uncontaminated ratio). Additionally, we derive an expression for estimating the true but unobserved CSF WBC in traumatic LP cases such that the existing atraumtic CSF WBC guidelines may be used. Finally, we present a Bayesian approach to incorporate non-zero CSF red blood cell (RBC) counts and suggest that this biologically-motivated assumption underlying S-B is likely not clinically relevant for the majority of patients.

Discovery of the spectacular Dueling Dinosaurs and other significant dinosaur localities from remote and isolated exposures of the Hell Creek Formation in central Montana highlight the complexity of establishing stratigraphic context and correlating Hell Creek Formation fossil localities located outside of the type area. This is particularly problematic for the lower two-thirds of the formation, which generally lacks reliable biostratigraphic or magnetostratigraphic zonation and has no dated ash beds. To address these enduring issues for one of the most significant Upper Cretaceous terrestrial fossil-bearing units in North America, detailed stratigraphic sections were established on the Murray Ranch and on McGinnis Butte in central Montana and correlated with other published Hell Creek Formation localities via magnetostratigraphy, biostratigraphy, and radioisotopic dating of ash beds. Results indicate that the K-Pg boundary is not exposed in the study area, however high-precision U-Pb CA-TIMS zircon ages for two newly discovered ash beds (66.929 {+/-} 0.020 Ma and 66.850 {+/-} 0.026 Ma, 2{sigma} internal uncertainties) bracketing the Dueling Dinosaurs locality provide the first absolute ages for the lower portion of the Hell Creek Formation, anywhere. Bayesian age-stratigraphic modelling places the Dueling Dinosaurs locality at 66.897 +0.023/-0.028 Ma and suggest that the age of the base of the formation is [~]67.102 +0.710/-0.173 Ma (or older) in the study area. Comparison of stratigraphic architecture within the study area with published sections in the type area suggests that named sandstone marker horizons used for lithostratigraphic and sequence stratigraphic correlation in the type area have limited utility for regional correlation and need to be used with caution.

Perseverance rover recently discovered sedimentary rocks reddened by ferric oxides and peppered with bleached spots lacking these oxides. Some of these spots are associated with phosphate, iron sulfide minerals, and organic matter, and are regarded as "potential biosignatures", suggestive of microbial iron-and sulfate-reduction and organic matter oxidation. Similar mm-cm-scale "reduction spots" occur in many ancient "red beds" on Earth. Although terrestrial reduction spots are widely considered biogenic, the available evidence is not decisive, and the proposed microbial mechanism of spot formation has not been tested experimentally. Here, we report a successful laboratory demonstration of bleached spot-formation in ferruginous sediment. Mm-cm-scale rounded bleached spots appeared within weeks on the underside of anaerobic sand-ferrihydrite slurries inoculated with mixed microbial communities obtained from the reducing zones of Winogradsky columns. The spatial and temporal distribution of observed bleaching events, which did not occur in sterile controls, are best explained by a microbially induced process, and DNA sequencing confirms that bacteria of iron-reducing genera are abundant in the bleached areas. These results strongly support the longstanding hypothesis that microbial colonies can indeed generate visibly bleached reduction spots in ferruginous sediments and rocks. Further experiments are needed to establish whether and how non-biological processes can mimic these features, and to search for features that disambiguate biogenic and abiogenic reduction spots.

The aftermath of the Permian - Triassic crisis is characterized by ubiquitous occurrences of microbial sediments around the world. For instance, Triassic deposits of the Germanic Basin have shown to provide a rich record of stromatolites as well as of microbe-metazoan build-ups with non-spicular demosponges. Despite their paleoecological significance, however, all of these microbialites have only rarely been studied. This study aims to fill this gap by examining and comparing microbialites from the Upper Buntsandstein (Olenekian, Early Triassic) and the lower Middle Muschelkalk (Anisian, Middle Triassic). By combining analytical petrography (optical microscopy, micro X-ray fluorescence, Raman spectroscopy) and geochemistry ({delta}13Ccarb, {delta}18Ocarb), we show that all studied microbialites formed in hypersaline lagoons to sabkha environments. Olenekian deposits in Jena and surroundings and Anisian strata at Werbach contain stromatolites. Anisian successions at Hardheim, in contrast, host microbe-metazoan build-ups. Thus, the key-difference is the absence or presence of non-spicular demosponges in microbialites. After the Permian - Triassic crisis, the widespread microbialites (e.g., stromatolites/microbe-metazoan build-ups) possibly resulted from suppressed ecological competition and occupied the vacant ecological niche. It seems plausible that microbes and non-spicular demosponges had a mutualistic relationship and it is tempting to speculate that the investigated microbial-metazoan build-ups reflect an ancient evolutionary and ecologic association. Furthermore, both microbes and non-spicular demosponges may benefit from elevated salinities. Perhaps it was minor differences in salinities that controlled whether or not non-spicular demosponges could develop.

Breast cancer remains a dominant health risk for women globally with early detection a primary indicator for successful treatment and survival. Current approaches for diagnosis are invasive, costly, and accuracy can be improved. Breath testing using volatile organic compounds (VOCs) as biomarkers presents an exciting avenue for non-invasive cancer diagnosis. However, breath sampling for cancer diagnosis has not yet delivered reliable biomarkers or technology. This is, in-part due to methodology, which introduces confounding factors when attempting to scale to diverse patient populations. We utilize a novel approach to human clinical breath sampling, in which we quantify breath volatile flux. Breath volatile flux considers inhaled air alongside exhaled air to generate a dynamic breath profile which enhances our ability to identify compounds metabolized in humans. We present a novel breath collection platform into which breast cancer clinic patients, in a pilot study of 60 women, provided 5 mins duration breath samples for analysis by gas chromatography mass spectrometry (GC-MS). GC methods targeted a suit of 11 previously identified compounds alongside non-targeted scans. When examining the data across the entire cohort, butanone was the only significantly altered (increased) breath volatile and was able to separate benign tumour and cancer patients from normal patients. However, patient age was observed as a primary confounding factor and reduced the accuracy of butanones diagnostic potential. When age was controlled for, chloroform, styrene and isopropyl alcohol acted as indicators of breast cancer health status. Furthermore, once age was accounted for and cancer patients were identified, grade of cancer was indicated by chloroform and DMS fluxes. Using the top 5 discriminate compounds and receiver operator curves we were able to identify cancer from normal patients with area under the curve of 93.4%, grade 2/3 cancers from normal patients with 97.6% AUC, and benign from normal patients with 90.5% AUC. This study suggests that volatile flux measurements from breath allows successful identification, and separation of, cancer, benign tumour and healthy patients.

In recent years radioligand therapy has emerged as an effective treatment modality for various solid malignancies, with pharmacokinetic modeling being routinely used for absorbed dose calculation and patient-specific therapy planning. Exemplary time-activity curves of FAP-targeted radioligands in a mouse model are accurately fitted by a sum of right skew biexponential distributions with four adjustable parameters in total. This type of modeling function is versatile and also suitable for conventional drugs. For further insight, an auxiliary equation is derived that relates tumor clearance to FAP expression and the radioligand dissociation constant.

Many extant demosponges, especially the non-spicular taxa, incorporate foreign detritus in their spongin or chitinous skeletons. This supposed energy-efficient way of skeleton construction is, however, rarely known in the fossil record. In this study, based on careful petrographic analyses using standard optical microscopy, cathodoluminescence and fluorescence microscopy, and a three-dimensional reconstruction, a fossil from the Cambrian Stage 4 of Xuzhou City, Jiangsu Province, China, is established as a sediment-agglutinating sponge Psammolectospongia beiwangensis gen. et sp. nov. These fossils encrust stromatolitic microbialites and are often surrounded by Girvanella mats. This succession of microbialites and sponge fossils was developed in a turbulent hydrodynamic condition after the deposition of edgewise conglomerates. P. beiwangensis possesses labyrinthine skeletons with an architecture similar to that of some stromatoporoids, such as Stromatopora and Syringostromella, although dissepiments are absent in the Cambrian fossil. The skeleton of P. beiwangensis is mainly composed of packed silt-to sand-sized detritus grains and skeletal fragments of other animals, while in some places, it can contain various proportions of micrites. The morphology and skeletal composition of P. beiwangensis indicate an affinity to an agglutinating demosponge, which mainly constructed its skeleton using agglutinated and incorporated sediments, while the spongin skeleton was able to be biomineralized like that of Vaceletia. This study is the first report of a sponge fossil that mainly built its skeleton using foreign detritus, and it expands our knowledge about the physiology and ecological behaviors of early Paleozoic demosponges.

Metastatic dissemination in lung cancer (LC) and other solid tumors is influenced not only by tumor-intrinsic biology and immune-inflammatory responses, but also by the physical properties of the vascular system through which circulating tumor cells (CTCs) migrate. Peripheral arterial disease (PAD), particularly when manifesting as aneurysmal dilation, is frequent among long-term smokers and is associated with chronic vascular inflammation and altered hemodynamics. We hypothesized that PAD-related vascular remodeling and rheological alterations may influence tumor metastatic capacity. Through a retrospective analysis of 976 patients diagnosed with both cancer and arteriopathy between 2018 and 2024, a cohort of 120 individuals with concomitant aneurysmal and neoplastic disease was identified. Demographic, biochemical, and pathological variables were examined, and metastatic burden at diagnosis was compared with that of an unselected LC population from the same institution and with literature-reported data. We focused on non-small cell lung cancer (NSCLC) as a well-characterized biological model and developed a phenomenological biophysical framework linking inflammation-driven changes in blood viscosity to metastatic competence. A Monte Carlo simulation approach was used to estimate metastasis probability under control and PAD-like rheological conditions. Despite marked male predominance and high smoking exposure, the study cohort exhibited an unexpectedly low metastatic burden, with 13.3% of patients presenting metastatic disease at diagnosis and only 7.6% showing extrathoracic dissemination, compared with an expected rate of approximately 30%. Partition analysis identified arteriopathy as the strongest predictor associated with reduced metastatic dissemination. The rheological model indicated that once inflammation exceeds a critical threshold, increased blood viscosity and disturbed flow patterns may act as a mechanical filter impairing CTC extravasation. Monte Carlo simulations supported this threshold-dependent mechanism, showing an approximately 50% reduction in predicted metastatic rates in PAD-like conditions compared with controls. Collectively, these findings suggest that chronic PAD and aneurysmal vasculopathy may reshape the circulatory microenvironment, with NSCLC providing a mechanistically interpretable framework for a transition from a metastasis-permissive to a metastasis-restrictive rheological regime.

Fossilization, or the transition of an organism from the biosphere to the geosphere, is a complex mechanism involving numerous biological and geological variables. Bacteria are one of the most significant biotic players to decompose organic matter in natural environments, early on during fossilization. However, bacterial processes are difficult to characterize as many different abiotic conditions can influence bacterial efficiency in degrading tissues. One potentially important variable is the composition and nature of the sediment on which a carcass is deposited after death. We experimentally examined this by decaying the marine shrimp Palaemon varians underwater on three different clay sediments. Samples were then analyzed using 16S ribosomal RNA sequencing to identify the bacterial communities associated with each clay system. Results show that samples decaying on the surface of kaolinite have a lower bacterial diversity than those decaying on the surface of bentonite and montmorillonite, which could explain the limited decay of carcasses deposited on this clay. However, this is not the only role played by kaolinite, as a greater proportion of gram-negative over gram-positive bacteria is observed in this system. Gram-positive bacteria are generally thought to be more efficient at recycling complex polysaccharides such as those forming the body walls of arthropods. This is the first experimental evidence of sediments shaping an entire bacterial community. Such interaction between sediments and bacteria might have contributed to arthropods exquisite preservation and prevalence in kaolinite-rich Lagerstatten of the Cambrian Explosion.

The scientific utility of Eugene Dubois Pithecanthropus erectus (P.e.) Skullcap (Trinil 1), Femur I (Trinil 3) and associated paleontological specimens has been impaired for over a century by questions about their provenience. Firsthand accounts and contemporaneous field photographs, presented here, extensively document the site geology and discovery history. The P.e. specimens and numerous-other fossils were unearthed in 1891-1893 from small excavations dug into a flat-lying bonebed exposed near the seasonal low-water level of the Solo River along its incised left embankment. Dubois on-site supervisors specified that the two P.e. fossils came from a [~]0.2-m-thick bonebed subunit traced at a single elevation for [~]12m from the 1891 Skullcap pit ([~]30m2) to the 1892 Femur-discovery excavation and across an enlarged 1892-1893 trench ([~]170m2). The depositional co-occurrence of the finds is supported by key documentation: the supervisors letters to Dubois about Femur I; his initial reporting to the Indies government; 1892-1893 accounts about expanding excavation of the Femur I stratum; Dubois 1891-1893 government submissions and 1894-1896 publications; confirmation by the Selenka Expedition in 1907-1908; Dubois annotations on unpublished site photographs; and a letter he wrote the year he died. Field studies in the 1930s to 1970s confirmed the essential aspects of the site geology. The bonebed of 1891-1893 contained fossils referable to the extinct Trinil fauna species Axis lydekkeri, Duboisia santeng and Stegodon trigonocephalus. The Selenka Expedition excavations had a similar assemblage in the same stratigraphic position which they named the Hauptknochenschicht. The bonebed was thin bioclast-rich gravelly volcaniclastic sandstone with taphonomic and sedimentary features indicating an unusual origin. Bioclasts range from proboscidean craniums and logs to rat teeth, freshwater mollusc shells and leaves. The terrestrial-vertebrate skeletal elements are overwhelmingly disarticulated and frequently broken. Their surfaces are little-abraded by fluvial transport. The bone fossilization is quite uniform. More than one-hundred ungulate individuals perished. No evidence has been found of hominin- or terrestrial-carnivore involvement. The bioclasts varied in density from place-to-place and vertically, and were matrix supported in the bonebed. No substantial internal depositional hiatus was reported. In combination with Trinils paleogeographic context, these features implicate a catastrophic mortality of ungulates in a population aggregation along the floodplain of a perennial paleo-river, followed by lahar-flood transport and deposition of gravel-size lithic- and biotic-materials. Trinil provides evidence favoring a broad archaic-hominin presence in southern Sundaland. The Trinil fauna is a lynch-pin in a long-lasting paleobiogeographic association between H. erectus and certain lineages of large bovids, cervids, proboscideans, rhinoceros, suids and tiger. The bonebeds paleogeographic setting exemplifies the stratovolcanic drainages that H. erectus occupied for >0.8 million years in Java, including the watershed of a marine delta [~]150km east of Trinil, a volcanic island [~]100km north of Trinil, and areas to its west for 500km (where species associated with Trinil H. erectus occur). In the Java Sea (Sunda Shelf), seismic data image immense Pleistocene river- and coastal-terranes which archaic hominins and other large-mammals, like those at Trinil, might have inhabited.

Glioblastoma multiforme is an aggressive brain tumor with the lowest survival rate of any human cancer due to its invasive growth dynamics. These dynamics result in recurrent tumor pockets hidden from medical imaging, which standard radio-treatment and surgical margins fail to cover. Mathematical modeling of tumor growth via partial differential equations (PDE) is well-known; however, it remains unincorporated in clinical practice due to prolonged run-times, inter-patient anatomical variation, and initial conditions that ignore a patients current tumor. This study proposes a glioblastoma multiforme tumor evolution model, GlioMod, that aims to learn spatiotemporal features of tumor concentration and brain geometry for personalized therapeutic planning. A dataset of 6,000 synthetic tumors is generated from real patient anatomies using PDE-based modeling. Our model employs image-to-image regression using a novel encoder-decoder architecture to predict tumor concentration at future states. GlioMod is tested in its simulation of forward tumor growth and reconstruction of patient anatomy on 900 pairs of unseen brain geometries against their corresponding PDE-solved future tumor concentrations. We demonstrate that spatiotemporal context achieved via neural modeling yields tumor evolution predictions personalized to patients and still generalizable to unseen anatomies. Its performance is measured in three areas: (1) regression error rates, (2) quantitative and qualitative tissue agreement, and (3) run-time compared to state-of-the-art numerical solvers. The results demonstrate that GlioMod can predict tumor growth with high accuracy, being 2 orders of magnitude faster and therefore suitable for clinical use. GlioMod is provided as an open-source software package, which includes the synthetic tumor data generated from the patients in our study.

Oncology therapeutic development continues to be plagued by high failure rates leading to substantial costs with only incremental improvements in overall benefit and survival. Advances in technology including the molecular characterisation of cancer and computational power provide the opportunity to better model therapeutic response and resistance. Here we use a novel approach which utilises Bayesian statistical principles used by astrophysicists to measure the mass of dark matter to predict therapeutic response. We construct "Digital Twins" of individual cancer patients and predict response for cancer treatments. We validate the approach by predicting the results of clinical trials. Better prediction of therapeutic response would improve current clinical decision-making and oncology therapeutic development.

Histological analysis of teeth can yield information on an organisms growth and development, facilitating investigations of diet, health, environment, and long-term responses to selective pressures. In the Americas, an extraordinary abundance of Late Pleistocene fossils including teeth has been preserved in petroleum seeps, constituting a major source of information about biotic changes and adaptations at the end of the last glacial period. However, the usefulness of these fossils for histological studies is unclear, due to the unknown taphonomic effects of long-term deposition in petroleum. Here, we compare histological and chemical analyses on dire wolf (Canis dirus) teeth obtained from two different environments, i.e. a petroleum seep (Rancho La Brea tar pits, California) and a carstic sinkhole (Cutler Hammock sinkhole, Florida). Optical and scanning electron microscopy (SEM) together with X-ray diffraction (XRD) analysis revealed excellent preservation of dental microstructure in the seep sample, and the petroleum-induced discoloration was found not to interfere with the histological and chemical examination. By comparison, teeth from the sinkhole sample showed severe degradation and contamination of the dentine by exogenous substances. These results indicate that petroleum seep assemblages are useful, or even ideal, environments for preserving the integrity of fossil material for chemical and histological analysis.

Four environments (swamp, shallow lake, alluvial flood plain, and lagoon) from the Lower Magdalena River Basin were studied for palynofacies quantitative characterization. Each environment has been described based on four criteria: palynomorph assemblage, organic matter concentration, organic matter palynological composition, and organic particle morphology. Shallow lakes palynological assemblages are dominated by composite and grass pollen. The POM (particulate organic matter) morphology is characterized by a maximum at {Phi} 5 class (silt), and it has a sphericity histogram with bimodal distribution (peaks at 0.1 and 0.5/0.6). From a composition point of view, POM is mainly opaque amorphous materials. POM concentration is usually lower than 0.1%. Swamp environments palynological assemblages are dominated by grass pollen with a slightly smaller amount of composite pollen. The POM is dominated by finely dispersed amorphous and indeterminate "other" types (organo-mineral gel ?), depending on the oxidation degree. The swamp concentration of organic matter a few centimeters below the water-sediment interface varies between 0.1% and 0.3%. Below that, organic concentration is usually lower than 0.1%. Lagoon assemblages are rich in species and specimens, but assemblages are highly variable. Main components are either finely dispersed amorphous or plant cuticular/epidermal or amorphous homogeneous and heterogeneous or fungal remains. Peat lithology is rich in mangrove pollen, while clay assemblages are dominated by composites, grass, and water plants together with Botryococcus algal remains. Lagoon sediments are the richest in POM concentration, with values between 0.13% and 1% (excluding peats). Regarding particle size and shape, in this environment, they show a trend to decrease in grain size from {Phi} 1 to {Phi} 2 class (sand) dominated assemblages to {Phi} 5 to {Phi} 6 class (silt) dominated assemblages from base to top. Elongated shapes are abundant, with 30% to 50% of particles in the tabloid to elongated tabloid classes. Alluvial - fluvial flood basin samples are often barren in palynomorphs and organic matter. Occasionally present grass pollen and fungal remains. The POM, when present, is mainly of organo-mineral gel type and has a bimodal grain size distribution, with a minor peak at {Phi} 7 class (v.f.silt) and a major peak at {Phi} 4 to {Phi} 2 class (c. silt to f. sand). Significant changes in quantitative palynofacies occur within the top few meters of the cores, representing the last 1000 yr of sedimentation in the area. These changes are related to shifts in climate, from colder to warmer conditions or from dry to wet periods, most probably linked with E.N.S.O. A short dry and cold period related to the "Little Ice Age" was identified in the Ayapel and Cienaga de El Medio cores.

Precambrian metasediments provide a unique archive for understanding Earths earliest biosphere, however traces of microbial life preserved in ancient rocks are often controversial. In this study we leveraged several micro- to nano-scale techniques to study filamentous structures previously reported in clastic sediments of the 3.22 Ga Moodies Group, Barberton Greenstone Belt, S. Africa. We performed petrographic, mineralogical, electron microprobe, confocal fluorescence and electron microscopy analyses of these structures in order to evaluate their biogenicity and syngenecity. We also examined drill core samples of deep-water iron formations from the 2.46 Ga Joffre member of the Brockman Iron Formation (Hamersley Basin, W. Australia) to better understand their potential biogenicity. In both cases, we aimed to resolve primary vs. secondary mineral assemblages and their relation to filamentous or sedimentary structures. In the Moodies Group samples, filamentous structures were resolved by confocal imaging and revealed to be crosscut by later metamorphic phases, highlighting their syngenetic nature. Three-dimensional imaging reveals that while the filamentous structures are not necessarily associated with grain boundaries (e.g., as organic coatings), they form both sheets and filaments, complicating their interpretation but not ruling out a biological origin. No organic microstructures appeared to be preserved in our Dales Gorge samples. We also examined the possible application of electron paramagnetic resonance spectroscopy (EPR) to carbonaceous matter in ancient silica-rich matrices, similar to Bourbin et al. (2013), using samples from the Brockman iron formation. While resonance associated with organic matter was largely unresolvable in the Brockman iron formation samples due to their low organic matter contents, large effects on the EPR spectra were apparent stemming from the presence of magnetic iron minerals, highlighting the need to carefully consider sample composition in EPR analyses targeting ancient organic matter. Collectively, this study highlights the added value of micro- to nano-scale techniques as applied to Precambrian metasediments containing traces of ancient life, for example in revealing the pre-metamorphic emplacement and three-dimensional structure of filaments in the Moodies Group, but also the potential drawbacks and pitfalls, such as the case of strong magnetic mineral interference in EPR analysis of organic matter in trace abundance in the Dales Gorge.