• The timescale of early land plant evolution

      Morris, JL; Puttick, MN; Clark, JW; Edwards, D; Kenrick, P; Pressel, S; Wellman, CH; Yang, Z; Schneider, H; Donoghue, PCJ (National Academy of Sciences of the United States of America, 2018-03-06)
      Establishing the timescale of early land plant evolution is essential for testing hypotheses on the coevolution of land plants and Earth’s System. The sparseness of early land plant megafossils and stratigraphic controls on their distribution make the fossil record an unreliable guide, leaving only the molecular clock. However, the application of molecular clock methodology is challenged by the current impasse in attempts to resolve the evolutionary relationships among the living bryophytes and tracheophytes. Here, we establish a timescale for early land plant evolution that integrates over topological uncertainty by exploring the impact of competing hypotheses on bryophyte−tracheophyte relationships, among other variables, on divergence time estimation. We codify 37 fossil calibrations for Viridiplantae following best practice. We apply these calibrations in a Bayesian relaxed molecular clock analysis of a phylogenomic dataset encompassing the diversity of Embryophyta and their relatives within Viridiplantae. Topology and dataset sizes have little impact on age estimates, with greater differences among alternative clock models and calibration strategies. For all analyses, a Cambrian origin of Embryophyta is recovered with highest probability. The estimated ages for crown tracheophytes range from Late Ordovician to late Silurian. This timescale implies an early establishment of terrestrial ecosystems by land plants that is in close accord with recent estimates for the origin of terrestrial animal lineages. Biogeochemical models that are constrained by the fossil record of early land plants, or attempt to explain their impact, must consider the implications of a much earlier, middle Cambrian–Early Ordovician, origin.
    • The Potential Science and Engineering Value of Samples Delivered to Earth by Mars Sample Return

      Beaty, DW; Grady, MM; McSween, HY; Sefton-Nash, E; Carrier, BL; Altieri, Y; Amalin, Y; Ammannito, E; Anand, M; Benning, LG; et al. (iMOST, 2018-08-14)
      Return of samples from the surface of Mars has been a goal of the international Mars science community for many years. Affirmation by NASA and ESA of the importance of Mars exploration led the agencies to establish the international MSR Objectives and Samples Team (iMOST). The purpose of the team is to re-evaluate and update the sample-related science and engineering objectives of a Mars Sample Return (MSR) campaign. The iMOST team has also undertaken to define the measurements and the types of samples that can best address the objectives. Seven objectives have been defined for MSR, traceable through two decades of previously published international priorities. The first two objectives are further divided into sub-objectives. Within the main part of the report, the importance to science and/or engineering of each objective is described, critical measurements that would address the objectives are specified, and the kinds of samples that would be most likely to carry key information are identified. These seven objectives provide a framework for demonstrating how the first set of returned martian samples would impact future martian science and exploration. They also have implications for how analogous investigations might be conducted for samples returned by future missions from other solar system bodies, especially those that may harbor biologically relevant or sensitive material, such as Ocean Worlds (Europa, Enceladus, Titan) and others.
    • Eocene greenhouse climate revealed by coupled clumped isotope-Mg/Ca thermometry

      Evans, D; Sagoo, N; Renema, W; Cotton, LJ; Müller, W; Todd, JA; Kumar Saraswati, P; Stassen, P; Ziegler, M; Pearson, PN; et al. (PNAS, 2018-01-22)
      Past greenhouse periods with elevated atmospheric CO2 were characterized by globally warmer sea-surface temperatures (SST). However, the extent to which the high latitudes warmed to a greater degree than the tropics (polar amplification) remains poorly constrained, in particular because there are only a few temperature reconstructions from the tropics. Consequently, the relationship between increased CO2, the degree of tropical warming, and the resulting latitudinal SST gradient is not well known. Here, we present coupled clumped isotope (Δ47)-Mg/Ca measurements of foraminifera from a set of globally distributed sites in the tropics and midlatitudes. Δ47 is insensitive to seawater chemistry and therefore provides a robust constraint on tropical SST. Crucially, coupling these data with Mg/Ca measurements allows the precise reconstruction of Mg/Casw throughout the Eocene, enabling the reinterpretation of all planktonic foraminifera Mg/Ca data. The combined dataset constrains the range in Eocene tropical SST to 30–36 °C (from sites in all basins). We compare these accurate tropical SST to deep-ocean temperatures, serving as a minimum constraint on high-latitude SST. This results in a robust conservative reconstruction of the early Eocene latitudinal gradient, which was reduced by at least 32 ± 10% compared with present day, demonstrating greater polar amplification than captured by most climate models.
    • Rare earth elements in phoscorites and carbonatites of the Devonian Kola Alkaline Province, Russia: Examples from Kovdor, Khibina, Vuoriyarvi and Turiy Mys complexes

      Zaitsev, AN; Terry Williams, C; Jeffries, T; Strekopytov, S; Moutte, J; Ivashchenkova, OV; Spratt, J; Petrov, SV; Wall, F; Seltmann, R; et al. (Elsevier, 2014-09)
      he Devonian (ca. 385–360 Ma) Kola Alkaline Province includes 22 plutonic ultrabasic–alkaline complexes, some of which also contain carbonatites and rarely phoscorites. The latter are composite silicate–oxide–phosphate–carbonate rocks, occurring in close space-time genetic relations with various carbonatites. Several carbonatites types are recognized at Kola, including abundant calcite carbonatites (early- and late-stage), with subordinate amounts of late-stage dolomite carbonatites, and rarely magnesite, siderite and rhodochrosite carbonatites. In phoscorites and early-stage carbonatites the rare earth elements (REE) are distributed among the major minerals including calcite (up to 490 ppm), apatite (up to 4400 ppm in Kovdor and 3.5 wt.% REE2O3 in Khibina), and dolomite (up to 77 ppm), as well as accessory pyrochlore (up to 9.1 wt.% REE2O3) and zirconolite (up to 17.8 wt.% REE2O3). Late-stage carbonatites, at some localities, are strongly enriched in REE (up to 5.2 wt.% REE2O3 in Khibina) and the REE are major components in diverse major and minor minerals such as burbankite, carbocernaite, Ca- and Ba-fluocarbonates, ancylite and others. The rare earth minerals form two distinct mineral assemblages: primary (crystallized from a melt or carbohydrothermal fluid) and secondary (formed during metasomatic replacement). Stable (C–O) and radiogenic (Sr–Nd) isotopes data indicate that the REE minerals and their host calcite and/or dolomite have crystallized from a melt derived from the same mantle source and are co-genetic.
    • Triggers for the formation of porphyry ore deposits in magmatic arcs

      Wilkinson, JJ (Springer Nature, 2013-10-13)
      Porphyry ore deposits are the source of much of the copper, molybdenum, gold and silver used by humans. Porphyry ore typically forms in magmatic arcs above subduction zones. However, generation of the largest deposits is often restricted to specific arc segments and limited periods of time. Here, I outline a hierarchy of four key triggers that may be involved in the formation of large porphyry deposits. The first process is characterized by a cyclical enrichment of magmas with metals and water in the deep crust. Second, saturation of the magma with sulphide facilitates the concentration of metals into smaller volumes of material from which they can later be released. The third process is an efficient transfer of metals into hydrothermal fluids that are exsolved from the magmas. Finally, localized processes trigger the precipitation of ore minerals in the crust. Although some or all of these processes must act in concert to generate large ore deposits, I argue that sulphide saturation of the magma is the most important step and that this can explain the temporal and spatial distribution of ores. Consequently, the fingerprint of sulphide saturation in igneous rocks could be used to identify those parts of magmatic arcs that are particularly predisposed to ore formation.
    • “What’s in a Name?” The Taxonomy & Phylogeny of Early Homo

      Galway-Witham, Julia (Ubiquity Press, 2016-01-05)
      Hominin systematics, encompassing both taxonomy and phylogeny (Strait, 2013), has significant implications for how the evolution of species and traits are understood and communicated. Following a recent influx of fossils (e.g., Brown et al., 2004; Lordkipanidze et al., 2013; Villmoare et al., 2015a; Berger et al., 2015) the amount of diversity in fossil morphology has increased correspondingly. As researchers do not yet approach diversity in a uniform manner, the literature has been flooded with conflicting theories and methodologies (Strait, 2013). Particularly volatile has been the study of the origin of the genus Homo and the extent of variation therein: much controversy arises from conflicting views of the number of valid species subsumed within ‘early Homo’ given unspecified definitions of species and genera. Additionally, there is still a lack of understanding of the extent of and mechanism behind variation, especially within Hominina. The first section of the following paper addresses ‘how can species be identified?’ and ‘how should species be classified into higher taxa?’ The second section reviews the prevalent arguments used to systematise fossils frequently classified as ‘early Homo.’ It considers: the validity of Homo rudolfensis; the morphological, spatial & temporal overlap of earlier Homo with Homo ergaster; the systematic significance of the recently discovered LD 350-1; and finally, the appropriateness of ‘early Homo’ as an adaptive grade.
    • Glacial and gully erosion on Mars: A terrestrial perspective

      Conway, SJ; Butcher, FE; de Haas, T; Deijns, AA; M. Grindrod, P; Davis, JM (Elsevier, 2018-05-24)
      The mid- to high latitudes of Mars host assemblages of landforms consistent with a receding glacial landscape on Earth. These landforms are postulated to have formed >5 Ma under a different climate regime when Mars' orbital obliquity was on average 10° higher than today. Here, we investigate the spatiotemporal relationship between gullies and glacial landforms, both common in the mid-latitudes. Gullies are kilometre-scale landforms with a source alcove, transportation channel, and depositional apron. The glacial landforms comprise (1) extant viscous flow features (VFF) that extend from the base of crater walls into the interior of crater floors and are widely interpreted as debris-covered glaciers containing extant ice, and (2) landforms such as arcuate ridges at the base of crater walls that have been interpreted as relicts of more recent, less extensive glacial advances focussed on crater walls. We measure headwall retreat associated with glacial landforms and date their host-craters to constrain minimum headwall retreat rates. We record headwall retreat rates up to ~102 m My−1 for the youngest suite of glacial landforms, equivalent to erosion rates of wet-based glaciers on Earth and to headwall retreat rates associated with martian bedrock gully systems. We find extensive evidence for a single erosional episode dating 5–10 Ma, which postdates emplacement of the majority of VFF but seems to predate formation of the gullies. We propose that the wet-based glacial episode was associated with glaciation focussed on the crater walls rather than melting of the glacial ice deposits on the crater floors (VFF). This is consistent with our observations of crater wall morphologies, including the presence of arcuate ridges consistent with terrestrial glaciotectonic features that require liquid water to form, textural alteration of the eroded bedrock surface consistent with ice-segregation and frost-shattering, and the presence of downslope pasted-on terrain, tentatively interpreted here as glacial till deposits sourced from glacial erosion of the crater wall. The pasted-on terrain is usually interpreted as a thicker, latitude-dependant mantle located on sloping terrain formed from airfall of ice nucleated on dust, but we suggest that it has been reworked by glaciation and is predominantly glacial in origin. Although our results cannot substantiate that gullies are produced by meltwater, the discovery of this wet glacial event does provide evidence for widespread meltwater generation in Mars' recent history.
    • Interspecific interactions through 2 million years: are competitive outcomes predictable?

      Liow, LH; Di Martino, E; Voje, KL; Rust, S; Taylor, PD (The Royal Society, 2016-08-31)
      Ecological interactions affect the survival and reproduction of individuals. However, ecological interactions are notoriously difficult to measure in extinct populations, hindering our understanding of how the outcomes of interactions such as competition vary in time and influence long-term evolutionary changes. Here, the outcomes of spatial competition in a temporally continuous community over evolutionary timescales are presented for the first time. Our research domain is encrusting cheilostome bryozoans from the Wanganui Basin of New Zealand over a ca 2 Myr time period (Pleistocene to Recent). We find that a subset of species can be identified as consistent winners, and others as consistent losers, in the sense that they win or lose interspecific competitive encounters statistically more often than the null hypothesis of 50%. Most species do not improve or worsen in their competitive abilities through the 2 Myr period, but a minority of species are winners in some intervals and losers in others. We found that conspecifics tend to cluster spatially and interact more often than expected under null hypothesis: most of these are stand-off interactions where the two colonies involved stopped growing at edges of encounter. Counterintuitively, competitive ability has no bearing on ecological dominance.
    • Diversification dynamics in freshwater bivalves (Unionidae) from the East African Rift

      Ortiz-Sepulveda, C; Stelbrink, B; Poux, C; Monnet, C; Albrecht, C; Todd, JA; Michel, E; Van Bocxlaer, B; Anon (SIAL, 2018-07-29)
      Invertebrates are exceptionally diverse, but declining because of anthropogenic changes to their habitat, as exemplified by freshwater bivalves in Europe and North America. Much less information is available for African freshwater bivalves, especially for Unionidae, which comprise 9 genera and ~40 nominal species, many of which are endemic to African ancient lakes. The phylogenetic position of most of these genera and species remains uncertain, and their conservation status unassessed. Here, we present preliminary results of phylogenetic studies on the Unionidae of the East African Rift. We integrate a phylogenetic backbone based on four gene fragments with (1) sampling information to examine geographic patterns of diversity and with (2) geometric morphometrics of shell shape to examine the relation between morphological disparity and molecular diversity. African Unionidae apart from ‘Cafferia’ form a monophyletic clade, and the basal splits in this clade occur between the reciprocally monophyletic genera Pseudospatha and Grandidieria, both of which are currently endemic to Lake Tanganyika. Mweruella, Nyassunio and Prisodontopsis are also monophyletic in the preliminary analyses as is Nitia, although this latter taxon is nested within Coelatura, which highlights the need of systematic revisions. Biogeographic analyses indicate a statistically significant North-to-South colonization of the East African Rift by Coelatura sensu lato. Beyond deep phylogenetic splits among individual clades, limited molecular differentiation is observed within most clades, calling for population genetic studies. Ongoing morphometric analyses suggest strong morphological differentiation among several clades, but substantial disparity in shell shape is observed within many clades, which needs further examination.
    • Variable Tl, Pb, and Cd concentrations and isotope compositions of enstatite and ordinary chondrites-Evidence for volatile element mobilization and decay of extinct 205 Pb

      Palk, C; Andreasen, R; Rehkämper, M; Stunt, A; Kreissig, K; Coles, B; Schönbächler, M; Smith, C (Wiley, 2017-10-23)
    • “Perspectives in Animal Phylogeny and Evolution”: A decade later

      Giribet, G; Edgecombe, GD; Fusco, G (University of Padova PressPadova, 2019-01-15)
      Refinements in phylogenomic methods and novel data have clarified several controversies in animal phylogeny that were intractable with traditional PCR-based approaches or early Next Gen analyses. An alliance between Placozoa and Cnidaria has recently found support. Data from newly discovered species of Xenoturbella contribute to Xenacoelomorpha being placed as sister group of Nephrozoa rather than within the deuterostomes. Molecular data reinforce the monophyly of Gnathifera and ally the longenigmatic chaetognaths with them. Platyzoa was an artefactual grouping, and deep relationships within Spiralia now depict Rouphozoa (= Gastrotricha + Platyhelminthes) as sister group to Lophotrochozoa, and Gnathifera (plus Chaetognatha) their immediate sister group. A “divide and conquer” strategy of subsampling clades to optimize gene selection may be needed to simultaneously resolve the many disparate clades of the animal tree of life
    • The systematic position of the enigmatic thyreophoran dinosaur Paranthodon africanus , and the use of basal exemplifiers in phylogenetic analysis

      Raven, TJ; Maidment, SC (PeerJ, 2018-03-20)
      The first African dinosaur to be discovered, Paranthodon africanus was found in 1845 in the Lower Cretaceous of South Africa. Taxonomically assigned to numerous groups since discovery, in 1981 it was described as a stegosaur, a group of armoured ornithischian dinosaurs characterised by bizarre plates and spines extending from the neck to the tail. This assignment has been subsequently accepted. The type material consists of a premaxilla, maxilla, a nasal, and a vertebra, and contains no synapomorphies of Stegosauria. Several features of the maxilla and dentition are reminiscent of Ankylosauria, the sister-taxon to Stegosauria, and the premaxilla appears superficially similar to that of some ornithopods. The vertebral material has never been described, and since the last description of the specimen, there have been numerous discoveries of thyreophoran material potentially pertinent to establishing the taxonomic assignment of the specimen. An investigation of the taxonomic and systematic position of Paranthodon is therefore warranted. This study provides a detailed re-description, including the first description of the vertebra. Numerous phylogenetic analyses demonstrate that the systematic position of Paranthodon is highly labile and subject to change depending on which exemplifier for the clade Stegosauria is used. The results indicate that the use of a basal exemplifier may not result in the correct phylogenetic position of a taxon being recovered if the taxon displays character states more derived than those of the basal exemplifier, and we recommend the use, minimally, of one basal and one derived exemplifier per clade. Paranthodon is most robustly recovered as a stegosaur in our analyses, meaning it is one of the youngest and southernmost stegosaurs.
    • R. V. Dingle Ostracod Collection: Natural History Museum, London

      Dingle, RV; Giles Miller, C; Jones, C (Copernicus Publications, 2012)
      The collection was donated to the Natural History Museum (NHM) between 2009 and 2011 and consists of 2534 slides. It comprises mainly marine ostracods of Jurassic to Holocene age from southern Africa (and its adjacent oceans), Antarctica and New Zealand. There is also a small collection of Quaternary non-marine ostracods from southwestern Africa, two sets of DSDP/ODP ostracods from the Southern Ocean, and one set of Cape Roberts Drilling Project (CRDP) ostracods from Victoria Land, East Antarctica. The individual slides in this collection have been computer registered. Further details of these can be found by inputting seach criteria based on information given in the paper to the NHM’s on-line catalogue at http://www.nhm.ac.uk/research-curation/collections/departmental-collections/palaeontology-collections/search/index.php.
    • A global assessment of Zn isotope fractionation in secondary Zn minerals from sulfide and non-sulfide ore deposits and model for fractionation control

      Mondillo, N; Wilkinson, JJ; Boni, M; Weiss, DJ; Mathur, R (Elsevier, 2018-11-15)
      We investigated extent and direction of Zn isotope fractionation in secondary zinc minerals formed during low temperature hydrothermal and/or supergene oxidation of primary sulfide deposits. Zinc isotope data have been obtained from non-sulfide zinc mineral separates (willemite - Zn2SiO4, smithsonite - ZnCO3, hemimorphite - Zn4(Si2O7)(OH)2·H2O, hydrozincite - Zn5(CO3)2(OH)6, and sauconite - Na0.3Zn3(Si,Al)4O10(OH)2·4H2O) collected from several Zn deposits in Ireland, Belgium, Poland, Namibia, Peru, Yemen and Zambia. The data are compared with Zn isotope compositions measured on Zn sulfides collected in the same areas and/or derived from the existing literature, to establish the controls of direction and likely extent of any fractionations. We find that willemite has the greatest compositional variability, with measured δ66ZnJCM-Lyon values ranging from −0.42 to 1.39‰, spanning the entire range of terrestrial variation in Zn isotopes recorded to date. Overall, significant fractionations in positive and negative directions are recorded relative to the precursor phase (primary sphalerite or an earlier secondary phase), with primary sphalerite falling in a relatively narrow range of isotopic values (approximately −0.1 to +0.4‰). Most of the data observed on willemite, hemimorphite and hydrozincite can be explained with a model of isotopic fractionation, in which partial dissolution of primary sphalerite is followed by precipitation of an initial secondary phase that preferentially incorporates heavy Zn isotopes. Smithsonite, instead, preferentially incorporates light Zn isotopes. This reflects the variation in the Zn-x bond strengths of these secondary phases with respect to the original sulfides. We also observed that isotope compositions do not depend only on the difference between the fractionation factors of the involved phases but also on the amount of the secondary mineral precipitated after dissolution of primary sulfide, and that the greatest fractionations occur when only small amounts of secondary mineral are precipitated. Progressive precipitation from migrating fluids that form phases enriched in heavy zinc isotopes would lead to a gradual decrease in the δ66Zn values of such phases, and the fluids involved, in time and space. Strong negative isotopic shifts are almost only observed for late crystallizing phases, such as those in vugs. These are interpreted to reflect precipitation from residual, isotopically-light fluids that are the inevitable highly-fractionated product of the above-described process. Where a more complete replacement of primary sulfide has occurred, such as in the high-grade core of non-sulfide zinc orebodies, there is limited net isotopic fractionation because dissolved primary zinc is nearly quantitatively reprecipitated locally. In addition, in only one case (Yanque, Peru) we observed that the fringes of non-sulfide zinc deposit were characterized by isotopically fractionated compositions, with highly negative values implying extensive precipitation (earlier, or elsewhere) of isotopically heavy secondary phases. The higher-grade ore zones, where complete breakdown of primary sulfides and quantitative reprecipitation of zinc have occurred, show instead less fractionated compositions.
    • The molecularization of centipede systematics

      Edgecombe, GD; Giribet, G; Fusco, G (Padova University Press, 2019-01)
      The injection of molecular data over the past 20 years has impacted on all facets of centipede systematics. Multi-locus and transcriptomic datasets are the source of a novel hypothesis for how the five living orders of centipedes interrelate but force homoplasy in some widely-accepted phenotypic and behavioural characters. Molecular dating is increasingly used to test biogeographic hypotheses, including examples of ancient vicariance. The longstanding challenge of morphological delimitation of centipede species is complemented by integrative taxonomy using molecular tools, including DNA barcoding and coalescent approaches to quantitative species delimitation. Molecular phylogenetics has revealed numerous instances of cryptic species. “Reduced genomic approaches” have the potential to incorporate historic collections, including type specimens, into centipede molecular systematics.
    • Biesiespoort revisited: a case study on the relationship between tetrapod assemblage zones and Beaufort lithostratigraphy south of Victoria West

      Day, M; Rubidge, BS (University of the Witwatersrand Johannesburg, 2018-12)
      The relationship between the tetrapod assemblage zones of the South African Karoo Basin and the lithostratigraphic divisions of the Beaufort Group is well-established, and provides an independent means of dating fossil occurrences. However, this relationship may not be consistent across the basin; a discrepancy exists between the historical tetrapod assemblages in the vicinity of Victoria West, Northern Cape Province, and the expected tetrapod assemblage zones based on mapped geology. In order to examine this disconnect, we collected fossils at two localities close to Biesiespoort railway station, a locality that was visited on a number of occasions by Robert Broom. Our fossil samples support the biostratigraphic determinations of Broom and thus confirm that the stratigraphic extent of the biozones at these localities differs from their type areas further south. The reasons for this are unclear but could be related to the northward younging of the lithological units, implying complex depositional processes, or result from difficulties in mapping. Nevertheless, caution should be exercised when using mapped geology near Victoria West as a guide to the age of fossils found there.
    • The Lyell Collection at the Earth Sciences Department, Natural History Museum, London (UK)

      Sendino, MCSL (Pensoft Publishers, 2019-02-19)
      This paper provides a quantitative and general description of the Lyell Collection kept in the Department of Earth Sciences at the Natural History Museum of London. This collection started to be built by the eminent British geologist Sir Charles Lyell (1797-1875) in 1846 when the first specimen reached the Museum. The last one entered in 1980 donated by one of Lyell’s heirs. There are more than 1700 specimens, mainly hand specimens with 93% of the fauna and flora from the Cenozoic of the Macaronesian archipelagos of the Canaries and Madeira. Those specimens that belong to the Lyell Collection with certainty have been databased and imaged. Currently they are being geo-referred automatically with the rest of the site geo-references at the NHM. This collection could be increased by a couple of dozen more specimens with those specimens located in the same drawers, but they do not have collector details. The work of data collection of these specimens was implemented over a year from 2016 to 2017, including annelids; brachiopods; bryozoans; echinoderms; scyphozoans; bivalves; gastropods; scaphopods; trilobites; plants; reptiles; fishes; and mammals. Access to the specimen-level data is available through the NHM data portal with the images associated. This is the first time that a description of the Fossil Lyell Collection dataset is available in the literature.
    • The alteration history of the Jbilet Winselwan CM carbonaceous chondrite: An analog for C-type asteroid sample return

      King, A; Russell, S; Schofield, P; Humphreys-Williams, E; Strekopytov, S (Wiley, 2018-12-13)
      Jbilet Winselwan is one of the largest CM carbonaceous chondrites available for study. Its light, major, and trace elemental compositions are within the range of other CM chondrites. Chondrules are surrounded by dusty rims and set within a matrix of phyllosilicates, oxides, and sulfides. Calcium‐ and aluminum‐rich inclusions (CAIs) are present at ≤1 vol% and at least one contains melilite. Jbilet Winselwan is a breccia containing diverse lithologies that experienced varying degrees of aqueous alteration. In most lithologies, the chondrules and CAIs are partially altered and the metal abundance is low (<1 vol%), consistent with petrologic subtypes 2.7–2.4 on the Rubin et al. (2007) scale. However, chondrules and CAIs in some lithologies are completely altered suggesting more extensive hydration to petrologic subtypes ≤2.3. Following hydration, some lithologies suffered thermal metamorphism at 400–500 °C. Bulk X‐ray diffraction shows that Jbilet Winselwan consists of a highly disordered and/or very fine‐grained phase (73 vol%), which we infer was originally phyllosilicates prior to dehydration during a thermal metamorphic event(s). Some aliquots of Jbilet Winselwan also show significant depletions in volatile elements such as He and Cd. The heating was probably short‐lived and caused by impacts. Jbilet Winselwan samples a mixture of hydrated and dehydrated materials from a primitive water‐rich asteroid. It may therefore be a good analog for the types of materials that will be encountered by the Hayabusa‐2 and OSIRIS‐REx asteroid sample‐return missions.
    • Glastonbury Lake Village Revisited: A Multi-proxy Palaeoenvironmental Investigation of an Iron Age Wetland Settlement

      Hill, T; Hill, G; Brunning, R; Banerjea, R; Fyfe, R; Hogg, A; Jones, J; Perez, M; Smith, D (Taylor & Francis, 2019-01-14)
      Glastonbury Lake Village is one of the most iconic late prehistoric wetland settlements in Europe. A new excavation in the core of Glastonbury Lake Village, for the first time since 1907, provided the opportunity for sampling of deposits associated with occupation of the site and for reconstructing the environmental conditions before the settlement was constructed. The results of a detailed multiproxy study are presented, including palaeoecological proxies (Coleoptera, plant macrofossils, diatoms, pollen, non-pollen palynomorphs), geoarchaeological methods (soil micromorphology), supported by new radiocarbon determinations. The results highlight how the difficult process of creating a settlement in a wetland was achieved, both within structures and in the spaces around them. Evidence for grain storage within the macrofossil assemblages, and the presence of animals on the settlement reflected in coleopteran assemblages and non-pollen palynomorphs has refined our understanding of the interaction between the settlement and the neighbouring dryland.