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<jats:title>Abstract</jats:title> <jats:p> Twenty taxa of fossil plants are described from the Sangonghe Formation (Lower Jurassic) of the Haojiagou section in the Junggar Basin, Xinjiang, NW China. The Sangonghe flora consists of Equisetales, ferns, bennettitaleans, ginkgoes, conifers and gnetales, but is dominated by ferns. It is a low-species-diversity but extraordinary flora as it has a high proportion (45%) of thermophilous or arid-tolerant (xerophilous) elements, in comparison to 0% in the underlying Badaowan Formation and <jats:italic>c.</jats:italic> 2% in the overlying Xishanyao Formation. These thermophilous or arid-tolerant (xerophilous) elements include <jats:italic>Marattiopsis asiatica</jats:italic> Kawasaki, <jats:italic>Phlebopteris polypodioides</jats:italic> Brongniart and <jats:italic>Dictyophyllum</jats:italic> sp. (ferns), <jats:italic>Otozamites leckenbyi</jats:italic> Harris, <jats:italic>Otozamites</jats:italic> sp., <jats:italic>Zamites</jats:italic> sp. and <jats:italic>Dictyozamites</jats:italic> sp. (bennettitaleans), <jats:italic>Brachyphyllum</jats:italic> ( <jats:italic>Hirmeriella</jats:italic> ?) sp. (conifers) and <jats:italic>Cadmisega ephedroides</jats:italic> Krassilov and Bugdaeva (gnetales). Based on the geological ranges of the known species and comparisons with coeval floras in Eurasia, the age of the Sangonghe flora is Toarcian (Early Jurassic). The flora reveals a climatic warming and aridification event that occurred during the Toarcian in the Junggar Basin. Palaeontological (including palaeobotanical and palynological), sedimentological and geochemical data demonstrate that warming and aridification occurred widely across the north of China during the Toarcian, and that this might be the response of the terrestrial ecosystem to the Toarcian Oceanic Anoxic Event. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> The middle Mesozoic of the southern Junggar Basin is a source of abundant Late Triassic–Jurassic non-marine and Early Jurassic marine–littoral bivalves. The bivalve chronology provides a framework for dating the strata and documents Early Jurassic transgressions and the end-Triassic mass extinction in the Junggar Basin. The first occurrences (FOs) and last occurrences (LOs) of <jats:italic>Utschamiella</jats:italic> cf. <jats:italic>tungussica</jats:italic> and <jats:italic>Utschamiella</jats:italic> cf. <jats:italic>obrutschevi</jats:italic> lie in the basal upper Rhaetian. The FOs of <jats:italic>Ferganoconcha sibirica</jats:italic> , <jats:italic>Ferganoconcha subcentralis</jats:italic> , <jats:italic>Unio manasensis</jats:italic> , <jats:italic>Unio mirabilis</jats:italic> and <jats:italic>Waagenoperna</jats:italic> are at, and the FOs of <jats:italic>Margaritifera isfarensis</jats:italic> , <jats:italic>Tutuella rotunda</jats:italic> and <jats:italic>Tutuella chachlovi</jats:italic> adjoin, the base of the middle Sinemurian. The LOs of <jats:italic>Yananoconcha hengshanensis</jats:italic> and <jats:italic>Waagenoperna</jats:italic> are at the Lower–Middle Jurassic boundary. The LOs of <jats:italic>Psilunio</jats:italic> , <jats:italic>Cuneopsis</jats:italic> and <jats:italic>F</jats:italic> . <jats:italic>subcentralis</jats:italic> are near the Middle–Upper Jurassic boundary. Non-marine bivalves disappeared in the late Rhaetian, due to a sudden Norian–Rhaetian temperature drop. New forms did not return until the Sinemurian, when the climate warmed. The transgressions created low-relief terrestrial environments, in which organisms including bivalves thrived, leading to the formation of large quantities of coal, oil and gas. The Junggar Basin shifted from Arctic to subtropical latitudes in the Northern Hemisphere between the Early and Middle Jurassic. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Junggar Basin, northwest China, hosts continuous and well-exposed Late Triassic and Jurassic continental strata. Extensive coal, oil and gas deposits occur within the basin, and together with the high palaeolatitude locality and continental records of several Mesozoic geological events, make the sedimentary successions globally important. This special publication focuses on these successions, presenting recent advances in palaeontology, geology, and palaeoenvironments. The contents span various topics, including studies of fauna, flora, stratigraphy, geochemistry, palaeogeography, palaeoclimate, petroleum reservoir quality, the end-Triassic mass extinction, the Toarcian Oceanic Anoxic Event, Triassic-Jurassic seasonal freezing and True Polar Wander. To provide continuity throughout the various papers, where possible, bed numbers for all stratigraphic units are provided, enabling findings to be compared among studies and tested in the future. This special publication highlights that the sediments of the Junggar Basin provide important long-term records of continental life and environmental changes through the Triassic and Jurassic.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> Newly discovered foliage of <jats:italic>Rhaphidopteri</jats:italic> s <jats:italic>zhouii</jats:italic> sp. nov. from the Lower Jurassic Sangonghe Formation at the Haojiagou section in the Junggar Basin of Xinjiang, northwestern China, is investigated based on morphological characters and cuticular structure. The new species has anisotomically divided leaves and linear ultimate segments with a single vein; amphistomatic cuticle, with epidermal cells that are similar both on the upper and lower surfaces but more regular on the upper surface; stomata that are distributed densely on the lower cuticle and sparsely and confined to two bands near the lateral margin on the upper cuticle; and anomocytic stomata that are longitudinally oriented with four to six subsidiary cells of irregular shape and size. This is the first report of the genus <jats:italic>Rhaphidopteris</jats:italic> from Xinjiang. The gross morphology and epidermal characters of the new species improves our understanding of the morpho-heterogenus <jats:italic>Rhaphidopteri</jats:italic> s. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> The vast, widely exposed terrestrial (lacustrine to fluvial) Upper Triassic–Jurassic (except Tithonian) successions of the Junggar Basin not only record most of the stratigraphic boundaries of the Upper Triassic and Jurassic, including the Triassic–Jurassic boundary and the Hettangian–Sinemurian, Sinemurian–Pliensbachian, Pliensbachian–Toarcian, Lower–Middle Jurassic, Middle–Upper Jurassic and Oxfordian–Kimmeridgian boundaries, but also record a range of geological, organic, palaeogeographic and palaeoclimatic events known to have happened globally in the Late Triassic and Jurassic. The Triassic–Jurassic boundary is placed in the stratigraphic interval of the first occurrence of <jats:italic>Retitriletes austroclavatidites</jats:italic> and <jats:italic>Callialasporites dampieri</jats:italic> and the last occurrence of <jats:italic>Lunatisporites rhaeticus</jats:italic> . The end-Triassic mass extinction is characterized by the disappearance of most of the sporomorph and macro-plant taxa. The end-Triassic mass extinction occurred before the first occurrence of the sporomorph <jats:italic>Cerebropollenites thiergartii</jats:italic> , and ended after its appearance when life began to revive. The Junggar Basin was situated at a high latitude during the Late Triassic–Early Jurassic Pliensbachian ‘hothouse’ and ‘greenhouse’ periods. The Late Triassic–Mid Jurassic Bajocian was humid and warm, and rich in coal swamps, except the Toarcian, which yields little coal because it was relatively warmer and drier. It became arid from the early Late Jurassic Oxfordian. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> The International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) has set up 25 commissions and working parties looking into various facets of volcanoes, some of these being joint investigations with other research organizations such as IASPEI (the International Association of Seismology and Physics of the Earth's interior) ( <jats:uri xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.iavceivolcano.org/commissions-networks/">https://www.iavceivolcano.org/commissions-networks/</jats:uri> - accessed 11 July 11, 2023). One of these commissions focuses on ‘Cities and Volcanoes’. The primary focus of IAVCEI is research in volcanology, efforts to mitigate volcanic disasters, and primary research into related disciples such as igneous geochemistry and petrology. However, the Cities and Volcanoes Commission has the specific aim of providing linkages between the volcanic community and emergency managers. It is intended to serve as a conduit for the exchange of ideas between ‘volcanic cities’, and to promote multi-disciplinary applied research involving the collaboration of physical and social scientists and city officials. This book is a contribution from the Cities and Volcanoes Commission and the stated aim of the editors was to encourage the exchange of experiences on volcanic islands to identify best practice in hazard assessment, monitoring techniques and risk mitigation strategies. They wished to encourage multidisciplinary contributions that observe, quantify, or model hazard in volcanic islands and in the surrounding coastal areas. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> In the Junggar Basin, northwestern China, the mass extinction-related strata at the base and top of the Triassic have been well studied, but the biostratigraphy and vegetation patterns of the Middle–Late Triassic sediments are comparatively poorly resolved. Here we investigate Middle–Late Triassic successions of the Dalongkou Section in the southern Junggar Basin for palynostratigraphy and vegetation patterns. Three palynological abundance zones are proposed here: the <jats:italic>Aratrisporites</jats:italic> Abundance Zone (Middle Triassic), the <jats:italic>Dictyophyllidites</jats:italic> - <jats:italic>Aratrisporites</jats:italic> Abundance Zone (latest Middle to early Late Triassic) and the <jats:italic>Lycopodiacidites</jats:italic> - <jats:italic>Stereisporites</jats:italic> informal abundance zone (Late Triassic). A review of previous records of the <jats:italic>Fukangichthys</jats:italic> Fauna indicates that this vertebrate fossil assemblage is stratigraphically located within the uppermost part of the Karamay Formation and is Middle Triassic in age. The revised dating of this and other faunas are further used to constrain the palynological zones in the Junggar Basin. Although the palynoflora is consistently dominated by non-striate bisaccate pollen (produced by seed ferns and/or conifers) in the studied section, spores record a distinctive abundance increase during the late Middle Triassic. Spore taxon abundance changes indicate a vegetational shift from a Middle Triassic-early Late Triassic community characterized by abundant lycophytes (likely <jats:italic>Annalepis</jats:italic> and <jats:italic>Pleuromeia</jats:italic> ) to a Late Triassic ecosystem with abundant dipteridaceous ferns (e.g. <jats:italic>Dictyophyllum</jats:italic> ) in the Junggar Basin and across North China. This study updates Triassic biostratigraphy in the Junggar Basin, and sheds light on temporal floral changes in this basin and elsewhere in North China during the Middle to Late Triassic. </jats:p> <jats:p content-type="supplementary-material"> Supplementary material at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" specific-use="dataset is-supplemented-by" xlink:href="https://doi.org/10.6084/m9.figshare.c.6655485">https://doi.org/10.6084/m9.figshare.c.6655485</jats:ext-link> </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Lahars are energetic flows of loosely consolidated volcanic debris and water, which have occurred frequently after rainfall events on St Vincent in the Eastern Caribbean since the April 2021 explosive phase of the 2020-21 eruption of La Soufriere volcano. Using scientific observations and information from social media, we have constructed a detailed timeline of 25 lahar events that occurred during 2021, and summarised lahar impacts and losses. 20 mm daily rainfall on a river catchment is (and remains) sufficient to result in a lahar. We used this threshold, with field estimates of lahar volumes, to conduct both an island-wide assessment of potentially impacted locations using the LAHARZ model, and a detailed reconstruction of one lahar event, using the dynamic model LaharFlow. A simplified catchment hydrology approach with runoff ratios typical for the Caribbean showed good agreement with observations of flow properties near the coast.</jats:p> <jats:p>Lahars will continue to be an important hazard in St Vincent into the future, and our modelling approach can assess future lahar impacts and provide early warnings. Social media provided key information about lahars and impacts, and allowed communities to alert each other. Future hazard mitigation should strengthen links between communities and with national risk management.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> We apply dynamical models to estimate the rheological properties of magma and lava during the 2021–22 eruption of La Soufrière Volcano, St Vincent. Analysis of the emplacement of a lava coulée gives viscosities in the range 0.94 × 10 <jats:sup>10</jats:sup> Pa s to 5.97 × 10 <jats:sup>10</jats:sup> Pa s. A static Bingham model gives a yield strength of 4.1 × 10 <jats:sup>5</jats:sup> Pa. A dynamical model of conduit flow during the explosive phase of the eruption gives a viscosity range from 1.2 × 10 <jats:sup>7</jats:sup> to 2.3 × 10 <jats:sup>9</jats:sup> Pa s. A petrological model of magma viscosity in the source region falls in the range 10 <jats:sup>2</jats:sup> to 10 <jats:sup>3</jats:sup> Pa s. The very high viscosity of the lava is attributed to the presence of a remnant degassed and partially crystallized magma from previous eruptions that occupied the shallow conduit–vent system prior to onset of the 2021 explosive eruptions. Gas-rich magma pushed this degassed remnant magma out over a three-month period at a steady rate of about 1.2 m <jats:sup>3</jats:sup> s <jats:sup>−1</jats:sup> and the explosive phase began when volatile-rich and much lower viscosity magma reached the surface. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> Real-time Seismic Amplitude Measurement signals and eruption cloud height measurements were used to estimate peak intensities of 40 explosive events during the 8–22 April 2021 activity of La Soufrière volcano. We estimated magma supply rates and erupted volumes in each explosion, characterized uncertainty by stochastic modelling and identified four eruptive stages. Stage 1 included an intense period of 9.5 hours with 11 explosive events with peak eruption intensity between 2000 and 4000 m <jats:sup>3</jats:sup> s <jats:sup>−1</jats:sup> and magma supply rate reaching 828 m <jats:sup>3</jats:sup> s <jats:sup>−1</jats:sup> . Twelve high-intensity explosions ( <jats:italic>c.</jats:italic> 4000 m <jats:sup>3</jats:sup> s <jats:sup>−1</jats:sup> ) occurred in Stage 2 with average magma supply rate of 251 m <jats:sup>3</jats:sup> s <jats:sup>−1</jats:sup> . Stage 3 involved both declining intensity and magma supply rate and lengthening repose periods between explosions. Stage 4 involved three much weaker explosions. The total erupted volume of magma is estimated at 38.5 × 10 <jats:sup>6</jats:sup> m <jats:sup>3</jats:sup> (90% credible interval: [22.0 .. 61.9] × 10 <jats:sup>6</jats:sup> m <jats:sup>3</jats:sup> ) consistent with independent estimates from analysis of tephra deposits and volcano subsidence sourced at <jats:italic>c.</jats:italic> 6 km depth. The 150-fold increase in magma supply rate, from the preceding effusive phase to Stage 1 of the explosive phase, is attributed to replacement of very high-viscosity degassed magma occupying the shallow conduit system with new, lower-viscosity, volatile-rich magma from the magma chamber. </jats:p>