Integrated stratigraphical study of the Rhuddanian-Aeronian (Llandovery, Silurian) boundary succession in the Rheidol Gorge, Wales:A proposed Global Stratotype Section and Point for the base of the Aeronian Stage

The Rheidol Gorge section, approximately 17 km east of Aberystwyth, mid Wales, exposes a ca. 20 m-thick succession of Llandovery (Silurian) strata from the upper Rhuddanian Pernerograptus revolutus Biozone through the lower Aeronian Demirastrites triangulatus Biozone and basal Neodiplograptus magnus Biozone. The section records deposition under a range of bottom-water oxygenation states. The Rhuddanian-Aeronian boundary is located 0.8 m above an abrupt lithological change from predominantly organic-poor, bioturbated `oxic' mudrocks to an interval of black, richly graptolitic `anoxic' shales. The graptolite fauna through the boundary interval, including the local lowest occurrence of D. triangulatus, allows precise correlation with other parts of the world. Graptolite assemblages indicative of separate divisions in the underlying revolutus Biozone and of the lower and upper parts of the triangulatus Biozone are also present. Chitinozoans are relatively well preserved in the section and indicate the Spinachitina maennili Biozone throughout the boundary interval, as is widely the case. The results of carbon isotope analyses from organic matter indistinctly show the weak interval of positive shift in d13C org values through the Rhuddanian-Aeronian boundary interval, as observed globally, though local or regional processes appear largely to overprint the global signal. Overall, the excellent biostratigraphical record, well-documented local and regional stratigraphical context, historical significance, as well as easy access and assured longterm preservation, mean that the Rheidol Gorge section can be proposed as a strong candidate for a new Global Stratotype Section and Point for the base of the Aeronian Stage.. Silurian, Llandovery, Rhuddanian, Aeronian, Global Stratotype Section and Point, Graptolites, Chitinozoa, Carbon Isotope

The Great Acceleration is real and provides a quantitative basis for the proposed Anthropocene Series/Epoch

The Anthropocene was conceptualized in 2000 to reflect the extensive impact of human activities on our planet, and subsequent detailed analyses have revealed a substantial Earth System response to these impacts beginning in the mid-20th century. Key to this understanding was the discovery of a sharp upturn in a multitude of global socio-economic indicators and Earth System trends at that time; a phenomenon termed the ‘Great Acceleration’. It coincides with massive increases in global human-consumed energy and shows the Earth System now on a trajectory far exceeding the earlier variability of the Holocene Epoch, and in some respects the entire Quaternary Period. The evaluation of geological signals similarly shows the mid-20th century as representing the most appropriate inception for the Anthropocene. A recent mathematical analysis has nonetheless challenged the significance of the original Great Acceleration data. We examine this analytical approach and reiterate the robustness of the original data in supporting the Great Acceleration, while emphasizing that intervals of rapid growth are inevitably time-limited, as recognised at the outset. Moreover, the exceptional magnitude of this growth remains undeniable, reaffirming the centrality of the Great Acceleration in justifying a formal chronostratigraphic Anthropocene at the rank of series/epoch

The Anthropocene is a prospective epoch/series, not a geological event

The Anthropocene defined as an epoch/series within the Geological Time Scale, and with an isochronous inception in the mid-20th century, would both utilize the rich array of stratigraphic signals associated with the Great Acceleration and align with Earth System science analysis from where the term Anthropocene originated. It would be stratigraphically robust and reflect the reality that our planet has far exceeded the range of natural variability for the Holocene Epoch/Series which it would terminate. An alternative, recently advanced, time-transgressive ‘geological event’ definition would decouple the Anthropocene from its stratigraphic characterisation and association with a major planetary perturbation. We find this proposed anthropogenic ‘event’ to be primarily an interdisciplinary concept in which historical, cultural and social processes and their global environmental impacts are all flexibly interpreted within a multi-scalar framework. It is very different from a stratigraphic-methods-based Anthropocene epoch/series designation, but as an anthropogenic phenomenon, if separately defined and differently named, might be usefully complementary to it

Extraordinary human energy consumption and resultant geological impacts beginning around 1950 CE initiated the proposed Anthropocene Epoch

Growth in fundamental drivers—energy use, economic productivity and population—can provide quantitative indications of the proposed boundary between the Holocene Epoch and the Anthropocene. Human energy expenditure in the Anthropocene, ~22 zetajoules (ZJ), exceeds that across the prior 11,700 years of the Holocene (~14.6 ZJ), largely through combustion of fossil fuels. The global warming effect during the Anthropocene is more than an order of magnitude greater still. Global human population, their productivity and energy consumption, and most changes impacting the global environment, are highly correlated. This extraordinary outburst of consumption and productivity demonstrates how the Earth System has departed from its Holocene state since ~1950 CE, forcing abrupt physical, chemical and biological changes to the Earth’s stratigraphic record that can be used to justify the proposal for naming a new epoch—the Anthropocene

Earthing the Anthropos? From ‘socializing the Anthropocene’ to geologizing the social

Responding to claims of Anthropocene geoscience that humans are now geological agents, social scientists are calling for renewed attention to the social, cultural, political and historical differentiation of the Anthropos. But does this leave critical social thought’s own key concepts and categories unperturbed by the Anthropocene provocation to think through dynamic earth processes? Can we ‘socialize the Anthropocene’ without also opening ‘the social’ to climate, geology and earth system change? Revisiting the earth science behind the Anthropocene thesis and drawing on social research that is using climatology and earth systems thinking to help understand socio-historical change, this article explores some of the possibilities for ‘geologizing’ social thought. While critical social thought’s attention to justice and exclusion remains vital, it suggests that responding to Anthropocene conditions also calls for a kind of ‘geo-social’ thinking that relates human diversity and social difference to the potentiality and multiplicity of the earth itself

Response to Merritts et al. (2023): The Anthropocene is complex. Defining it is not

Merritts et al. (2023) misrepresent Paul Crutzen's Anthropocene concept as encompassing all significant anthropogenic impacts, extending back many millennia. Crutzen's definition reflects massively enhanced, much more recent human impacts that transformed the Earth System away from the stability of Holocene conditions. His concept of an epoch (hence the ‘cene’ suffix) is more consistent with the strikingly distinct sedimentary record accumulated since the mid-20th century. Waters et al. (2022) highlighted a Great Acceleration Event Array (GAEA) of stratigraphic event markers that are indeed diverse and complex but also tightly clustered around 1950 CE, allowing ultra-high resolution characterization and correlation of a clearly recognisable Anthropocene chronostratigraphic base. The ‘Anthropocene event’ offered by Merritts et al., following Gibbard et al. (2021, 2022), is a highly nuanced concept that obfuscates the transformative human impact of the chronostratigraphic Anthropocene. Waters et al. (2022) restricted the meaning of the term ‘event’ in geology to conform with usual Quaternary practice and improve its utility. They simultaneously recognized an evidence-based Anthropogenic Modification Episode that is more explicitly defined than the highly interpretive interdisciplinary ‘Anthropocene event’ of Gibbard et al. (2021, 2022). The advance of science is best served through clearly developed concepts supported by tightly circumscribed terminology; indeed, improvements to stratigraphy over recent decades have been achieved through increasingly precise definitions, especially for chronostratigraphic units, and not by retaining vague terminology

The Anthropocene monument:on relating geological and human time

In the Parthenon frieze, the time of mortals and the time of gods seem to merge. Dipesh Chakrabarty has argued that with the advent of the Anthropocene the times of human history and of the Earth are similarly coming together. Are humans entering the ‘monumental time’ of the Earth, to stand alongside the Olympian gods of the other geological forces? In this paper I first look at the cultural shifts leading to the modern idea of separate human and Earth histories. I examine the changing use of monuments to mediate between human and other temporalities. I explore the use of ‘stratigraphic sections’ as natural monuments to mark transitions between the major time units of Earth history, and the erection of intentional monuments nearby. I suggest that the Anthropocene, as a geological epoch-in-the-making, may challenge the whole system of monumental semiotics used to stabilise our way of thinking about deep time

Sedimentary Ways

This paper is a thought experiment to attune to the geo-physical and geo-political materialities of sediment, a terra-aqueous substance produced when the earth's continental surfaces intra-act with the atmosphere and are chemically transformed by it. The paper is framed by questions of how to engage more closely with the dynamics of earth systems and of how social and political agency emerges alongside earth forces. Sediment is important to such questions because it is the mechanism by which the earth recycles itself and is thick with the climatological and geological histories that have conditioned the possibility of life on the planet. While acknowledging the import of Deleuze and Guattari's metaphysics to such questions, the paper takes a material approach to them. It is based on field work in Bangladesh, but also traverses a range of scientific, historical and theoretical literature. It is arranged in four sections that loosely correspond to the sedimentary cycle. It follows sediment from chemical processes on rock surfaces in the Himalayas, to its lively travels in monsoonal rivers across flood plains to its eventual deposition and subterranean diagenesis. In each section, the paper discusses the material processes at work, their socio-political enmeshments and the theoretical implications of these intra-actions. The paper concludes that sediment serves as a reminder not only of close entanglements of geo-physical and geo-political becomings, but also of the profound indifference of earth systems to human affairs, and asks what this might mean for the re-imagination of politics

The position of graptolites within Lower Palaeozoic planktic ecosystems.

An integrated approach has been used to assess the palaeoecology of graptolites both as a discrete group and also as a part of the biota present within Ordovician and Silurian planktic realms. Study of the functional morphology of graptolites and comparisons with recent ecological analogues demonstrates that graptolites most probably filled a variety of niches as primary consumers, with modes of life related to the colony morphotype. Graptolite coloniality was extremely ordered, lacking any close morphological analogues in Recent faunas. To obtain maximum functional efficiency, graptolites would have needed varying degrees of coordinated automobility. A change in lifestyle related to ontogenetic changes was prevalent within many graptolite groups. Differing lifestyle was reflected by differing reproductive strategies, with synrhabdosomes most likely being a method for rapid asexual reproduction. Direct evidence in the form of graptolithophage 'coprolitic' bodies, as well as indirect evidence in the form of probable defensive adaptations, indicate that graptolites comprised a food item for a variety of predators. Graptolites were also hosts to a variety of parasitic organisms and provided an important nutrient source for scavenging organisms