The diet of an animal reflects its species’ ecology and local food availability and is often a key metric for monitoring the health and welfare of endangered species. However, determining diets across individuals and through space and time, is an inherent challenge within ecology, being expensive and time-intensive to accomplish with observations. Faeces offer the opportunity for non-invasive sample collection and can provide a snapshot of the ingested diet of the producer. In modern ecology, faecal samples have been a prime target for genetic analyses of diet and the gut microbiome. Here, however, we explore whether high molecular weight (HMW) n-alkane biomarkers extracted from faeces can provide useful information about diet. HMW n-alkanes are commonly employed in palaeoecological reconstructions. Combining faecal HMW n-alkane analyses with gut microbiome composition and detailed foraging data applied to two species of lemur in captivity with access to naturalized forest enclosures, we show that recovered HMW n-alkanes are completely dietary in origin and not correlated to the gut microbiome. Signatures are significantly different between our two focal lemur species and seasons, reflecting differences in ingested diet. It is possible to infer changes in the relative contributions of major plant parts, particularly leaves and fruits, based on the faecal HMW n-alkane concentrations. Whereas n-alkane signatures alone are perhaps ill-suited to pinpoint plant species in animals with complex herbivorous diets, when integrated with other complementary methodologies can provide a more comprehensive dietary reconstruction. HMW n-alkanes are simple to identify and measure; only requiring commonly available and relatively affordable analytical chemistry instruments (e.g. GC-FID). Beyond discussing downstream uses of our methodology to captive and wild lemurs, other primates and herbivorous and omnivorous animals globally, our pilot study hints at the promise of the organic geochemist’s toolkit applied to dietary ecology.

The Devonian sequence of the Cantabrian Zone of Northern Spain was deposited around an isolated group of islands (Armorican Terrane Assemblage - ATA) between the Laurussia and Gondwana supercontinents. The Candas Formation (Asturias) and equivalent Portilla Formation (Leon) represent one of the main episodes of reefal development within this sequence. Herein we report, for the first time, palynomorph assemblages recovered from these formations. Palynomorphs recovered from the Portilla Formation are poorly preserved and of high thermal maturity. They are dominated by dispersed spores but also contain abundant and diverse marine elements (acritarchs, chitinozoans and scolecodonts). Due to the challenging preservation, it is not possible to undertake an in-depth study of these assemblages. Palynomorphs recovered from the Candas Formation (members B and D) are exceptionally well preserved and of low thermal maturity. They are dominated by dispersed land plant spores, but also contain rarer marine elements (acritarchs, chitinozoans and scolecodonts). Member B spore assemblages belong with the triangulatus-catillus Assemblage Zone (catillus Subzone) of mid Givetian age. Member D spore assemblages belong with the langii-concinna Assemblage Zone of late Givetian to earliest Frasnian age. This is concordant with independent age dating based on conodonts and invertebrates. The spore assemblages are of North Gondwana aspect but exhibit evidence for distinct endemism. They are dominated by progymnosperm spores indicating a vegetation dominated by arborescent archaeopteridaleans and aneurophytaleans.

The Skagerrak-Centered large igneous province (SCLIP) was active 299 million years ago when Earth's climate transitioned into an interval of intensified glaciation. A link between the SCLIP and global climate change has been hypothesized but there is little direct evidence of concurrent volcanism and climate change in coeval sedimentary layers from the late Carboniferous to the early Permian. We combined carbon isotopes, mercury contents and isotopes, and elemental geochemistry of the Taiyuan Formation in the Hedong Coalfield, North China to identify two episodes of volcanism during the early and late Gzhelian (latest Carboniferous). Both episodes are marked by Hg enrichments, positive Delta 199Hg excursions and negative delta 13Corg excursions; only late Gzhelian volcanism was associated with reduced rates of continental weathering and was followed by global cooling. We hypothesize that the late Gzhelian volcanic episode had a greater environmental impact than that in the early Gzhelian because late Gzhelian volcanism was likely more intense and of longer duration. The SCLIP may have contributed to global cooling via the release of sulfate aerosols that results in atmospheric cooling and/ or from ocean fertilization and increased removal of organic carbon via the biological pump.

The ancient global warming event known as the Paleocene-Eocene Thermal Maximum (PETM, ∼56 Ma) provides an excellent case study for understanding the integrated Earth system response to massive carbon release. To evaluate its utility as a future analog, there is a need for accurate estimates not only for the durations of different phases, such as the onset duration, period of carbon release, and recovery timescale, but also for constraints on the source(s) of carbon. While the PETM corresponds to an interval of increased volcanic activity, the degree to which it was shaped by strong positive feedbacks may be particularly revealing about the sensitivity of the surficial carbon cycle to rapid warming. Studying the role of orbital forcing across the PETM has been essential to unlocking each of these key unknowns. Here, we review the study of orbital forcing in relation to the PETM, both in the application of cyclostratigraphy to constrain the duration and timing of the PETM and in the potential role of orbital forcing as a trigger or contributor for carbon release. We subsequently use new numerical simulations to evaluate feedback between PETM carbon release and orbital forcing.

Abstract. The concentrations of the major cations (esp., Ca2+, Mg2+) in Earth's oceans have undergone large-scale fluctuations in the geological past. This is important because the key geochemical properties of the marine environment that underpin the global carbon cycle – the aqueous carbonate system equilibria and solubility of solid calcium carbonate (CaCO3) – are heavily influenced by ion-pairing, which in turn depends on the activity of the major cations and anions. An accurate interpretation of marine proxies as well as the reconstruction of past states of ocean geochemistry and carbon cycle dynamics across geologic events requires that these effects are considered. However, most current global carbon cycle models use empirical carbonate system dissociation constants (K) fitted to laboratory experiments with present-day seawater major cation and anion concentrations. When simulations of global carbon cycling in the geologic past have been made, only relatively simplified empirical adjustments of the equilibrium constants (from Ben-Yaakov and Goldhaber [1974], Tyrrell and Zeebe [2004]) have been implemented when seawater composition differs from modern (e.g., Panchuk et al. [2008]). More commonly, no correction is made at all. Here we develop and evaluate a new scheme in the cGENIE Earth system model for correcting carbonate system equilibrium constants and account for variations in the dissolved calcium and magnesium concentrations in the ocean. We base our new parameterization on the MyAMI specific ion interaction model of Hain et al. [2015] and implement this in cGENIE by means of linear interpolation within a 4-dimensional parameter look-up table of pre- calculated carbonate system equilibrium constants. For modern SW composition, our implementation of MyAMI-based equilibrium constants yields no significant deviation from model results using empirically-based equilibrium constants, validating our look-up/interpolation approach. However, for simulations conducted under non-modern Mg/Ca, we find significant differences in carbon chemistry and CaCO3 saturation when using our new MyAMI-based equilibrium constants as compared to the existing (default) correction scheme. Specifically, our new MyAMI-based correction scheme exhibits a much lower sensitivity of surface ocean pH and calcite saturation state to a change in Mg/Ca from modern to Eocene, which were overestimated by the previous correction scheme. We can also expect that any bias in carbonate chemistry and CaCO3 saturation will affect the preservation and burial of CaCO3 in deep-sea sediments. We illustrate this by contrasting the ocean carbon inventory arising under Eocene Mg/Ca with the same total weathering (and hence CaCO3 burial) flux for the different possible equilibrium constant corrections. We find that the new MyAMI-based and previous default corrections give rise to a dissolved inorganic ocean carbon inventory 348 PgC higher and 950 PgC lower, respectively, relative to the same experiment conducted using empirical equilibrium constants without any Mg/Ca correction. Applying no correction at all for a different-from-modern Mg/Ca ratio in the ocean would appear to be better than applying a 'bad' correction but explicitly accounting for past dissolved calcium concentrations remains of fundamental importance. We provide this new carbonate system equilibria correction as an option in cGENIE.muffin version 0.9.64, and as standard in a completely new cGENIE code release – cGENIE.cookie v.0.9.

In Northern Spain there is a near complete sequence of Devonian rocks that accumulated around a relatively isolated land mass, the Armorican Terrane Assemblage, which was separated from Gondwana to the south and Laurussia to the north. The Lower to Middle Devonian transition records a dramatic facies change from carbonate to siliciclastic sedimentation. The Chotec Event, a global anoxic pulse that occurs just above the Lower-Middle Devonian boundary (392.5-393.1 Ma), has been identified within this transition. These strata are included in the Moniello and Naranco fms in Asturias and the equivalent Santa Lucia and Huergas fms in Leon. They are independently age-contrained based on conodont and invertebrate biotas. For the first time we describe palynomorph assemblages recovered from the Lower to Middle Devonian transition in Northern Spain. The assemblages contain terrestrial (spores) and marine (acritarchs, prasinophycean cysts, chitinozoans) elements, thus recording primary productivity on both the land and in the oceans. The older assemblages belong to the annulatus-sextantii Spore Zone and the younger assemblages the douglastownensis-eurypterota Spore Zone, which is concordant with the independent age constraints. Our analysis of the distribution and diversity of marine and terrestrial palynomorphs supports interpretations of the facies change associated with the Chotec Event as being related to a change to increased rainfall and terrestrial runoff. However, this change is associated with only limited taxon turnover in both land plant spores and marine phytoplankton and chitinozoans.

The (Basal) Choteč Event, first recognised in the 1980s in Czechia, is a globally widespread anoxic pulse associated with transgression and eutrophication just above the Emsian-Eifelian (Early-Middle Devonian) boundary (cycle 1c of the Johnson et al. [1985] Devonian eustatic sea-level curve). Despite being one of several anoxia-driven faunal turnovers during the Devonian, the Choteč Event remains poorly understood. The global reach, intensity, and duration of anoxia is not constrained and nor is it clear whether eutrophication had its “roots” in contemporary floral developments on land (as suggested for younger Devonian anoxic events).We present a geochemical (carbon isotopes; trace metals as proxies for redox and productivity; and major elements for the Chemical Index of Alteration [CIA] as a weathering proxy) and palynological study of the Cabonera section (León, Spain). This succession is part of an extensive Devonian sequence developed around isolated islands in the Armorican Terrane Assemblage that was located between the supercontinents Laurussia and Gondwana. Here, limestones of the Emsian-Eifelian Santa Lucia Formation are abruptly overlain by siltstones and shales belonging to the Eifelian Huergas Formation. This conodont- and brachiopod-constrained manifestation of the Choteč Event sees the onset of a gradual 4‰ negative δ13Ccarb excursion (CIE) consistent with records in other regions. The lower part of the Huergas Formation (Cabornera Bed) records a brief interval of anoxia (low Th/U, elevated V/Al and U/Al) at the same level that sees the onset of the negative CIE. This appears to have been accompanied by, or was perhaps driven by, greatly enhanced primary productivity, with enrichment factors (EFs) of Ba, and particularly Ni, Zn and P, all >>1. This brief burst of productivity and anoxia soon ended, with EFs falling

Eccentricity cycles in deep-sea paleoclimate records suggest that astronomical forcing notably altered global temperatures and carbon cycle dynamics. Because changes in the distribution of insolation alone cannot explain the observed climate variability, climate-carbon cycle feedbacks must have amplified the response. However, the carbon sources and sinks operating on orbital timescales are poorly understood, especially in absence of dynamic ice sheets as during the early Cenozoic. Here, we use an Earth system model to explore the impact of astronomical forcing on the organic carbon cycle and its expression in key paleoceanographic variables, building on Vervoort et al. (2024, https://doi.org/10.1029/2023pa004826) who outlined the role of inorganic carbon cycle feedbacks. Results demonstrate that subtle changes in marine organic carbon burial, driven by nutrient (phosphate, P) availability, can produce 400-kyr cycles of negative delta 13C excursions during periods of elevated pCO2 and reduced CaCO3 preservation, consistent with typical orbital variations in Paleocene records. The magnitude and phasing of the response to eccentricity forcing are determined by the balance between P release (via temperature-dependent rock weathering) and P removal (via oxygen-dependent sedimentary P retention). Because these processes are strongly influenced by the distribution of landmasses and shelves, paleogeography exerts a first-order control on the expression of astronomical cycles. We do not reproduce the high amplitude 100-kyr "hyperthermal events" of the early Eocene, but our model identifies two potential mechanisms to amplify global warming on orbital timescales: reduced organic carbon burial as well as enhanced kerogen weathering could increase CO2 during eccentricity maxima under favorable conditions.

The Paleocene-Eocene Thermal Maximum (PETM, 56 Ma) is perhaps the most extensively studied paleoclimate event of massive carbon release because the intense global warming and widespread ocean acidification bear resemblance to the predicted worst-case near-future Earth conditions. While emission rate and carbon source were different from today’s perturbation, valuable lessons can be learned from studying the PETM. For instance, whether climate or carbon cycle feedbacks amplify or mitigate the environmental disruption, and what feedback processes contributed to the global climate response. In this study, we quantify the magnitude and sign of ‘net’ carbon cycle feedbacks by integrating: (1) estimates of volcanic carbon emissions from the North Atlantic Igneous Province (active ~56 Ma and considered a major source of carbon release), and (2) the net global environmental response recorded in paleoclimate records such as δ18O (temperature), δ11B (ocean pH), and δ13C (carbon cycle). The difference between the environmental response to volcanic emissions alone and the recorded global response is attributed to feedback processes. Our Earth system model results suggest that carbon release from positive carbon cycle feedbacks (e.g. non-volcanic) likely approached or exceeded volcanic emission rates at the onset of the PETM, raising pCO2 by 1330 ppm and the global temperature by 4.4°C. The ‘net’ feedback emissions are negative during the PETM recovery. Carbon isotopes indicate that a sustained low emission flux of isotopically light carbon is required to slow down the δ13C recovery driven by organic carbon burial, potentially pointing to additional thermogenic or biogenic methane release during the recovery phase.

Milankovitch cycles recorded in marine sediments demonstrate the influence of astronomical forcing on Earth’s climate-carbon dynamics. Proxies suggest that during greenhouse climates, isotopically light carbon is released during episodic warm intervals (at eccentricity maxima) and re-sequestered during the following cooling (at eccentricity minima). However, the dominant carbon sources and sinks at play on orbital timescales remain unclear-- particularly when large dynamic ice sheets are absent as during the early Cenozoic. Methods: In an Earth system model (ESM), we apply 4-Myr-long transient astronomical forcing to examine how various climate-sensitive physical and (bio)geochemical processes respond and how this forcing is recorded in key oceanographic variables (temperature, pCO2, δ13C of DIC, and wt% CaCO3). Among others, we assess the impact of marine productivity, CaCO3 compensation, terrestrial weathering, organic matter burial, and phosphorus cycling. Results: Most processes are driven by changes in local conditions -controlled by obliquity and precession, but these high-frequency changes are converted to low-frequency eccentricity cycles expressed in pCO2, benthic δ13C, and wt% CaCO3 as a result of the lowpass filtering effect of the ocean reservoir. While the magnitude of early Cenozoic δ13C variability can be explained by astronomically forced input and burial fluxes of marine organic carbon alone, the dominant frequency and relative phasing of proxies highly depend on the geographic distribution of landmasses that control organic carbon fluxes. For example, only short eccentricity cycles of 100 kyr periodicity (as opposed to long 400 kyr cycles) are simulated in benthic δ13C under favorable paleogeographic configurations. In our model, the pCO2 and temperature response to orbital forcing is minimal, and eccentricity maxima coincide with enhanced preservation of CaCO3. In contrast, early Cenozoic proxies suggest a stronger temperature response and reduced CaCO3 preservation during warm intervals. Implication: Our results support the hypothesis that additional feedbacks that are not yet included here (e.g., terrestrial carbon or methane) were likely important controls during orbital-scale climate variability in greenhouse climates.

The early Eocene features distinctive coupling between biogeochemical cycles and climate, raising fundamental questions about Earth system functioning during major climate transitions and on orbital timescales. For instance, the transition to peak Eocene warmth is ushered in by a major shift in redox conditions and deep ocean circulation, while orbitally-paced hyperthermal events are associated with substantial carbon injections of uncertain origin. CO2 change is thought to play a key role in these events, yet despite recent progress, resolution is still lacking for most shorter time intervals. Here we present new, high-resolution boron isotope data from both benthic and planktic foraminifera that shed new light on Eocene carbon cycling. Using new approaches for conversion of boron isotope data to pH and CO2, we improve estimates of absolute CO2 concentrations and the change in CO2 over key events. Our data demonstrate a pervasive link between CO2 and climate in the Eocene hothouse over a range of timescales and provide novel constraints on carbon sources and climate sensitivity.

Mass extinctions have repeatedly perturbed the history of life, but their causes are often elusive. Ocean acidification has been implicated during Triassic-Jurassic environmental perturbations, but this interval lacks direct reconstructions of ocean pH. Here, we present boron isotope data from well-preserved fossil oysters, which provide evidence for acidification of ≥ 0.29 pH units coincident with a 2 ‰ negative carbon isotope excursion (the "main" CIE) following the end-Triassic extinction. These results suggest a prolonged interval of CO2-driven environmental perturbation that may have delayed ecosystem recovery. Earth system modelling with cGENIE paired with our pH constraints demonstrates this was driven by predominantly mantle-derived carbon. Ocean acidification therefore appears to be associated with three of the five largest extinction events in Earth history, highlighting the catastrophic ecological impact of major perturbations to the carbon cycle in Earth's past, and possibly Earth's anthropogenically perturbed future.

Multiple consecutive global environmental and biological changes during the Late Triassic Carnian Pluvial Episode (CPE; similar to 234-232 Ma) are thought to have been triggered by pulses of greenhouse gas emissions from Large Igneous Province (LIP) volcanism. However, the lack of high-resolution paired geochemical records of C-cycle disruption and volcanism pinned to cyclostratigraphic frameworks impedes estimates of the tempo of LIP emissions and associated climate changes. Our new astronomical timescale from terrestrial strata in the Jiyuan Basin (North China) reveals that the CPE lasted for approximately 1.65 Myr, encompassing four 405 kyr long eccentricity cycles. Each 405 kyr long eccentricity cycle was accompanied by coupled negative excursions of organic carbon isotopes (delta C-13(org)) and near-zero Delta Hg-199 values that indicate synchronous C-cycle perturbations and volcanic Hg deposition. This allows linking the consecutive environmental changes observed in the terrestrial succession of North China to distinct volcanic pulses of Wrangellia LIP. Our results show that in addition to the effects of Wrangellia LIP, orbital forcing, i.e. the 405 kyr long eccentricity, may have amplified the global climatic disturbances during the CPE.

A three-dimensional tubular fabric known as "vermiform microstructure" in Phanerozoic and Neoproterozoic carbonate microbialites has been hypothesized to represent the body fossil of nonspicular keratose demosponges. If correct, this interpretation extends the sponge body fossil record and origin of animals to ~890 Ma. However, the veracity of the keratose sponge interpretation for vermiform microstructure remains in question, and the origin of the tubular fabric is enigmatic. Here we compare exceptionally well-preserved microbialite textures from the Upper Triassic to channel networks created by modern microbial biofilms. We demonstrate that anastomosing channel networks of similar size and geometries are produced by microbial biofilms in the absence of sponges, suggesting the origin for vermiform microstructure in ancient carbonates is not unique to sponges and perhaps best interpreted conservatively as likely microbial in origin. We present a taphonomic model of early biofilm lithification in seawater with anomalously high carbonate saturation necessary to preserve delicate microbial textures. This work has implications for the understanding of three-dimensional biofilm architecture that goes beyond the current micro-scale observations available from living biofilm experiments and suggests that biofilm channel networks have an extensive fossil record.

In the last few decades, Geology courses, particularly in the Global North, have seen a decline in student enrolment. Geologists have linked this downturn to a lack of exposure to the subject at school and college level. This work seeks to understand the public’s relationship with Geology and draws on over 5,000 open-ended question responses to a survey disseminated in 2021. The survey asked both those who had, and had not, studied geology as a subject a series of questions in order to explore their perceptions of the discipline. Our findings indicate that individuals “outside” of geology see the subject as old fashioned, boring, and environmentally damaging; simply the study of rock samples with nothing new to be discovered from; and with poor job prospects outside of the oil and gas industry. Geologists who responded to the survey paint a picture of a broad, interdisciplinary subject, with vibrant employability opportunities—yet struggle to coherently and collectively describe this when asked, “what is geology?”. In addition to the identified perception of geology as boring, and notions of poor employability being a barrier to prospective students, diversity and inclusivity issues are highlighted as significant barriers by those who study geology. Our findings indicate that both geologists and the geology curriculum need to coherently describe what geology is more effectively. We need to develop and better communicate the subject’s interdisciplinary nature and links to critical societal issues, such as the role of responsible mineral extraction in the energy transition and the importance of geology in vital areas such as climate change science, water resource management, environmental conservation, and sustainable urban/built development. Finding new ways to show that, far from being boring, geology is a subject that can fundamentally change the way you see and interact with the world around you is of central importance to achieving this. Efforts to make the subject more equitable are also highlighted as being critical in creating a more inclusive and accessible discipline.

The deep-time geological record can provide insights into the processes and mechanisms of glacier retreat. Ice sheets of the Late Paleozoic Ice Age (LPIA) collapsed extensively during the early Artinskian (early Permian) approximately 290 million years ago through massive glacial melting that was associated with dramatic increases in global temperature, atmospheric pCO2, sea level, and resulted in profound changes in terrestrial plant distribution and diversity. A hypothesized mode of this extensively glacial melting is multiple large-scale volcanic events, but the causes and effects have not yet been clearly established because of the lack of detailed coeval records of volcanism and environmental changes. Here, we present a record of these events from an Artinskian terrestrial succession in the Liujiang Coalfield, North China. Our new U-Pb zircon dating, highresolution chemostratigraphy, and kerogen maceral data reveal that environmental changes (carbon cycle perturbation, wildfire, and continental weathering) in the region were intricately linked with the large-scale volcanism associated with the Tarim-II, Panjal and Choiyoi volcanic provinces. Our study shows that hypothesized volcanism and wildfire raised temperatures by releasing greenhouse gases, while the ensuing warming led to ice sheet melting, the release of terrestrial Hg and C and resulting Hg and C cycle anomalies.

Continental-scale expansion of the East Antarctic Ice Sheet during the Eocene-Oligocene Transition (EOT) is one of the largest non-linear events in Earth's climate history. Declining atmospheric carbon dioxide concentrations and orbital variability triggered glacial expansion and strong feedbacks in the climate system. Prominent among these feedbacks was the repartitioning of biogeochemical cycles between the continental shelves and the deep ocean with falling sea level. Here we present multiple proxies from a shallow shelf location that identify a marked regression and an elevated flux of continental-derived organic matter at the earliest stage of the EOT, a time of deep ocean carbonate dissolution and the extinction of oligotrophic phytoplankton groups. We link these observations using an Earth System model, whereby this first regression delivers a pulse of organic carbon to the oceans that could drive the observed patterns of deep ocean dissolution and acts as a transient negative feedback to climate cooling.

The Late Devonian Mass Extinction is the least understood of the ‘Big 5’ extinctions in virtually every aspect: timing, effects and causes - and there is little knowledge of the coupling of events on land and in the ocean. At one extreme, the marine crisis is viewed as a rapid, cataclysmic event at the Frasnian/Famennian boundary (the “Kellwasser Event”) followed by another crisis 13 Myr later (the “Hangenberg Event”). Alternatively, these Late and end-Devonian extinctions are viewed as a cumulative series of minor events, drawn out over the entire Devonian. Our project aims to resolve these through study of the spectacular Devonian sedimentary succession in northern Spain that is both remarkably complete and laterally extensive, providing a transect across an entire Devonian marine shelf from deep marine to near terrestrial environments. We present initial results from Piedrasecha, north of Léon. We analysed 47 samples spanning the Frasnian Nocedo Formation, and the Famennian-Tournasian (Carboniferous) Fueyo, Ermita and Baleas Formations. Combined geochemical and palynological analyses reveal:1) δ13Corg values are stable around -26‰ through the Frasnian and Famennian prior to a 2‰ negative shift associated with the onset of black mudstones at the base of the Baleas Formation (latest Famennian). This is likely a muted expression of the Hangenberg Event negative δ13Corg excursion.2) Redox proxies (Th/U, Mo/Al, V/Al and U/Al) indicate bottom waters remained oxygenated until the latest Famennian, when weakly dysoxic (at worst) conditions developed. There is no obvious expression of Kellwasser Event anoxia in this offshore setting, and only a weak manifestation of Hangenberg oxygen restriction.3) An order of magnitude shift in productivity proxy values (Ba/Al, Ni/Al, Zn/Al and P/Al) in the latest Famennian suggests that the Hangenberg Event is associated with increased primary productivity.4) Mercury is enriched in the upper Frasnian Nocedo Formation where it withstands normalisation to TOC (Hg/TOC values reach 388 ppb/wt%, similar to those reported for the Upper Kellwasser Horizon elsewhere). This mercury might derive from large igneous province volcanism and is potentially a chemostratigraphic marker for the Kellwasser Event, though we require better stratigraphic control to evaluate this. Significant Hg enrichments (up to 160 ppb) in the latest Famennian Baleas Formation do not withstand normalisation, as TOC reaches 4.7 wt% at this level. The succession is thermally mature and since TOC drops with thermal maturity, Hg/TOC values might be elevated in comparison to original values.5) Palynomorph assemblages are dominated by simple spores and Geminospora. The latter derives from the Mid-Late Devonian forest tree Archaeopteris. This suggests a rather homogenous vegetation typical of Late Devonian settings where successive extinctions stripped out diversity from terrestrial floras. However, it may be that in this distal section we are sampling spores that have been winnowed during transport. Work on other sections will enable us to test this.We have sampled 14 further sections providing a complete Devonian succession and with >500 samples in preparation we hope to resolve whether the Late and end-Devonian crises were the result of cumulative stresses, or were indeed cataclysmic events.

The ascendancy of dinosaurs to become dominant components of terrestrial ecosystems was a pivotal event in the history of life, yet the drivers of their early evolution and biodiversity are poorly understood.1,2,3 During their early diversification in the Late Triassic, dinosaurs were initially rare and geographically restricted, only attaining wider distributions and greater abundance following the end-Triassic mass extinction event.4,5,6 This pattern is consistent with an opportunistic expansion model, initiated by the extinction of co-occurring groups such as aetosaurs, rauisuchians, and therapsids.4,7,8 However, this pattern could instead be a response to changes in global climatic distributions through the Triassic to Jurassic transition, especially given the increasing evidence that climate played a key role in constraining Triassic dinosaur distributions.7,9,10,11,12,13,14,15,16 Here, we test this hypothesis and elucidate how climate influenced early dinosaur distribution by quantitatively examining changes in dinosaur and tetrapod "climatic niche space" across the Triassic-Jurassic boundary. Statistical analyses show that Late Triassic sauropodomorph dinosaurs occupied a more restricted climatic niche space than other tetrapods and dinosaurs, being excluded from the hottest, low-latitude climate zones. A subsequent, earliest Jurassic expansion of sauropodomorph geographic distribution is linked to the expansion of their preferred climatic conditions. Evolutionary model-fitting analyses provide evidence for an important evolutionary shift from cooler to warmer climatic niches during the origin of Sauropoda. These results are consistent with the hypothesis that global abundance of sauropodomorph dinosaurs was facilitated by climatic change and provide support for the key role of climate in the ascendancy of dinosaurs.