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<jats:p>The Morello Tectonic Unit in the Tuscan Apennines (Italy) represents the result of tectono-sedimentary deformation, occurring in the frontal part of the non-metamorphosed Ligurian Accretionary Wedge, which consists of ophiolitic slices imbricated with a sedimentary succession containing ophiolite-bearing sedimentary mélanges. Geological mapping, structural and stratigraphic observations, allow us to document that (i) the ophiolite-bearing sedimentary mélanges formed by gravitational reworking of material sourced from intrabasinal structural highs facing the oceanic basin environment from Jurassic to lower Eocene, before the middle Eocene accretion stage, and (ii) the ophiolitic tectonic slices represent the scraping off at shallow structural levels of part of these crustal oceanic highs sequence. The final internal architecture of the shallow frontal portion of the Ligurian Accretionary Wedge does not differ from those observed in metamorphosed orogenic belts and exhumed accretionary complexes throughout the world (e.g., blueschist and eclogite units of Western Alps). This suggests that to the classical model of subduction and metamorphism followed by accretion and mélange formation (i.e., underplating), a model in which frontal accretion and ophiolite mélange formation at a shallow level are followed by underthrusting and subduction can be added, providing additional constraints to a better reconstruction of orogenic belts and accretionary complexes evolution.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Ophiolites, melanges and blueschists collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists">https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists</jats:ext-link> </jats:p>

<jats:p> Early lithification of carbonate mud during the subaerial exposure stage, under semiarid conditions, has been proposed to facilitate dolomite formation. However, how the biogeochemical processes during subaerial diagenesis promote dolomite formation remains unclear. Here, we employ a multiproxy approach to investigate the process of dolomite formation by analyzing modern dolomite crusts forming in lagoon Brejo do Espinho (LBE). Petrological analysis reveals that the crusts comprise coexisting high-Mg calcite (HMC) and dolomite. Low Fe and Mn concentrations indicate the formation of dolomite under oxic conditions, while a higher Sr concentration in well-lithified crust suggests primary bacterial-induced dolomite precipitation. The Mg isotopic composition of the crusts exhibits a lighter value compared to that of modern sabkha dolomite, suggesting different dolomitization processes and Mg sources. More negative <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>δ</mml:mi> </mml:math> </jats:inline-formula> ¹³C values of the crusts than unlithified carbonate mud in LBE, indicating the incorporation of <jats:sup>13</jats:sup> C depleted organic carbon. The biogeochemical processes related to decaying organic matter during subaerial diagenesis generate partially oxidized organic matter that promotes Mg <jats:sup>2+</jats:sup> dehydration and enhances the dissolution of primary HMC, ultimately triggering the transition of HMC to dolomite or/and direct dolomite precipitation. The ancient "dolomite factory" operated through cyclic deposition of carbonate sediments and penecontemporaneous subaerial diagenesis. </jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Towards unravelling the ‘Dolomite Problem’: new approaches and novel perspectives collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/towards-unravelling-the-dolomite-problem">https://www.lyellcollection.org/topic/collections/towards-unravelling-the-dolomite-problem</jats:ext-link> </jats:p>

<jats:p>Studies of high pressure-low temperature (HP-LT) metamorphic complexes are critical for advancing our understanding of subduction processes, such as underplating, metamorphism, and exhumation. Detailed new U-Pb zircon data of blueschist-facies metasedimentary units at Pelion indicate two distinct, stratigraphically upright, and coherent structural slices, with (1) the South Pelion slice consisting of strata with Permian-Late Cretaceous zircon maximum depositional ages (MDAs) and (2) the North Pelion slice comprising strata with Triassic-Late Cretaceous zircon MDAs. Both slices have Late Cretaceous strata at the top of the section with cosmopolitan detrital zircon (DZ) signatures. Ages from zircon U-Pb rim overgrowths correlate with existing constraints from subduction-metamorphism during the Paleocene-Eocene, with a possible second stage recorded during Basal underplating in the Late Eocene-Oligocene. DZ provenance data and multi-dimensional scaling (MDS) comparisons demonstrate a tectono-metamorphic linkage between the Pelion rocks and the Cycladic Blueschist Unit (CBU), and between the southern Pelion Basement and the Cycladic Basement (CB). Protolith deposition for Pelion blueschist-facies rocks occurred during Permo-Carboniferous intra-arc extension and Adria-Pindos rifting. Our results show that the Pelion blueschist-facies rocks, representing lateral equivalents of the CBU, are comprised of two separate, coherent upper-crustal slivers that were underplated and metamorphosed during Hellenic subduction beneath the Pelagonian margin.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Ophiolites, melanges and blueschists collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists">https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists</jats:ext-link> </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.7008123">https://doi.org/10.6084/m9.figshare.c.7008123</jats:ext-link> </jats:p>

<jats:p>Multiple magnetic fabrics, referred to as F1–F5, were revealed through the anisotropy of magnetic susceptibility (AMS) in an Ocean Plate Stratigraphy (OPS) mélange of the Neoproterozoic–Cambrian Blovice accretionary complex, Bohemian Massif. The fabrics postdate the mélange formation and rotation of basalt blocks within the matrix and are interpreted in terms of a complex structural history of the mélange. Excluding local fabrics, the F1 fabric formed earlier along the mélange belt, recording shortening of the accretionary wedge front, whereas the higher-grade F4 fabric pervasively overprinted both blocks and matrix in the SW part of the belt, recording shearing and vertical shortening at deeper structural levels closer to a megathrust surface. The preservation of angular relationships between the F1 and F4 fabrics across different parts of mélange suggests that blocks were only strained and not rotated during deformation, exemplifying the notion that the OPS mélanges may be a product of deformation at very shallow levels. Finally, the F1–F5 fabrics may be viewed as snapshots in a protracted evolution of OPS mélanges, where earlier fabrics in basalt blocks may record the travel path of an oceanic plate from mid-ocean ridge towards the trench, before being overprinted in the accretionary wedge.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Ophiolites, melanges and blueschists collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists">https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists</jats:ext-link> </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.7008173">https://doi.org/10.6084/m9.figshare.c.7008173</jats:ext-link> </jats:p>

<jats:p> The Silurian was marked by repeated extinctions, carbon cycle volatility, and significant intervals of climatic change. The most notable of these events were the Ludfordian Lau/Kozlowskii extinction and associated Mid-Ludfordian Lau carbon isotope excursion, both of which have been linked to a period of global cooling and expanded reducing conditions in the global oceans. Here we present new data that characterize marine paleoredox conditions of the Prague Basin, a peri-Gondwanan terrane. This study utilizes iodine-to-calcium ratios to assess local redox conditions in a shallow water carbonate succession and iron speciation and redox-sensitive trace element concentrations to assess local redox conditions of a deeper water sequence. Consistently low values of I/Ca in the shallow water section suggest either persistent local low oxygen conditions or possibly diagenetic overprinting. Iron speciation data suggest that bottom water redox conditions in the deeper shelf setting were consistently anoxic with possible intermittent euxinia. Concentrations of redox-sensitive trace elements consistently higher than upper continental crust values also indicate persistent reducing conditions in the deeper part of the basin. These local redox proxy data from the Prague Basin, including trends in new pyrite sulfur isotope (δ <jats:sup>34</jats:sup> S <jats:sub>pyr</jats:sub> ) data, are consistent with findings that expansion of anoxic and/or euxinic oceanic conditions occurred. These data, derived from a mid-paleolatitude marine setting, fill an important gap in our current global dataset from this interval of the late Silurian. </jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Chemical Evolution of the Mid-Paleozoic Earth System and Biotic Response collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system">https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system</jats:ext-link> </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.7008107">https://doi.org/10.6084/m9.figshare.c.7008107</jats:ext-link> </jats:p>

<jats:p>The syntaxes at the eastern and western ends of the Himalaya located at the Tsangpo and Indus gorge regions provide examples of the interplay between tectonics and erosion. A previous borehole study along the Yarlung River in the Eastern Himalayan Syntaxis (EHS) reveals a ∼1 km thick sedimentary wedge upstream of the Tsangpo gorge with a &gt;2.5 Ma depositional age. However, mechanism of formation of this sedimentary wedge remains under debate. Here, we combine low-temperature thermochronology data and thermo-mechanical modelling to discuss how a sedimentary wedge formed at the highly eroded EHS. Our low-temperature thermochronology results show late Miocene fast cooling episodes focused at the Gyaca and Tsangpo gorges, which are interpreted to be related to coeval rifting at the former and rapid erosion and hot-crust upwelling at the latter. Constrained by the geological and geophysical observations, we apply thermo-mechanical models to illustrate the mechanism of formation of the sedimentary wedge and present high relief of the EHS. The numerical geodynamic model shows that localised erosion triggers middle ‘crust extrusion’ and regional topographic adjustment at the EHS.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change">https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change</jats:ext-link> </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.7008098">https://doi.org/10.6084/m9.figshare.c.7008098</jats:ext-link> </jats:p>

<jats:p>The concept of the Akiyoshi Orogeny emerged from the geological study of the overturned Akiyoshi Limestone. However, our understanding of the stratigraphy and geological structure of the siliceous-clastic rocks surrounding the Akiyoshi Limestone remains incomplete. In this study, we conducted a geological survey within the Beppu unit, distributed on the north of the Akiyoshi Limestone, revealing substantial-scale strata overturning even within the siliceous-clastic rocks, which formed as the upper section of the ocean plate stratigraphy within the accretionary complex. Additionally, the Tsunemori Formation, which is regarded as sediments of forearc or trench-slope basin, has also undergone overturning. Consequently, extensive overturned structures exist throughout the entire accretionary complex of the Mine-Akiyoshidai Area. To understand the mechanism behind these overturned structures within the accretionary complex, we focused on the collision and deformation resulting from the interaction between the accretionary wedge and a massive seamount along with the backstop. The overturning of the forearc or slope basin sediments suggested that post-accretion deformation along the large lateral fault may have occurred during the time of the collision between the South China and North China blocks. These tectonic events during and after accretion may represent the true nature of the Akiyoshi Orogeny.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Ophiolites, melanges and blueschists collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists">https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists</jats:ext-link> </jats:p>

<jats:p> The Early Devonian Xitun Vertebrate Fauna, represented by early members of crown sarcopterygians such as <jats:italic>Youngolepis</jats:italic> , <jats:italic>Diabolepis</jats:italic> , <jats:italic>Psarolepis</jats:italic> , <jats:italic>Achoania</jats:italic> , and <jats:italic>Styloichthys</jats:italic> , is mainly hosted in the Xitun Formation in Qujing area, East Yunnan of China. Despite numerous research articles describing taxa from this famous Lochkovian fauna and its sedimentary and tectonic environments, there is no objective and coherent interpretation of the palaeoenvironment in which these early vertebrates lived. Based on detailed field geological investigation in recent years in the surrounding areas of Qujing City and measurements from the Xitun Formation section, this paper focuses on the analysis of some geochemistry indices of major, trace, and rare earth elements to accurately elucidate the sedimentary environment of the Xitun Formation and deepen our understanding on the relationship between Early Devonian fishes and the environment. The analyses of the sensitive geochemistry indices of depositional and tectonic settings, sedimentary provenance, weathering, palaeoclimate, palaeosalinity, and palaeoredox conditions indicate that the Lower Devonian Xitun Formation in East Yunnan was mainly deposited in a shallow marine setting with three phases of seawater-freshwater influx under a warm and humid climate, and a stable, oxygen-rich condition, which promoted the flourishing of Early Devonian marine fishes <jats:bold>.</jats:bold> </jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Chemical Evolution of the Mid-Paleozoic Earth System and Biotic Response collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system">https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system</jats:ext-link> </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.7020642">https://doi.org/10.6084/m9.figshare.c.7020642</jats:ext-link> </jats:p>

<jats:p>The Tibetan Plateau, which is deformed by the collision between the Indian and Eurasian plates, is a natural laboratory to study intracontinental deformation related to northeastward growth of the Plateau. However, how and when the Tibetan Plateau propagated to its present-day margins remain unclear. The Qilian Shan and Haiyuan fault, which serve as the topographic and geological boundaries of high Plateau, are key to revealing the uplift and expansion of the Tibetan Plateau. Here, we present detrital apatite (U-Th)/He and reverse modelling results from the Laolongwan basin, which is interpreted as a pull-apart basin controlled by activity of the Haiyuan fault in the east portion of the Qilian Shan region. Our results reveal three stage tectono-thermal evolution of Qilian Shan: (a) late Jurassic to Cretaceous rapid exhumation; (b) late Cretaceous to middle Miocene tectonic quiescence period and (c) exhumation after middle Miocene. We suggest that the Jurassic to Cretaceous rapid exhumation might be related to the convergence of the Lhasa block with the Eurasian plate or regional extension during the Mesozoic closure of the Meso-Tethys, and the mid-Miocene accelerated exhumation was driven by Haiyuan fault activation related to the growth of the Tibetan Plateau to its northeastern margin.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change">https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change</jats:ext-link> </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.7018149">https://doi.org/10.6084/m9.figshare.c.7018149</jats:ext-link> </jats:p>

<jats:p>We report uplift and shortening rates from a late Neogene–Pleistocene deformation stage of the frontal fold-thrust belt and adjacent wedge-top in the Principal Cordillera of the southern Central Andes (33-39° SL). A structural model is presented based on integration of surface field data and subsurface 2D seismic sections. Shortening, uplift, and sedimentation rates were calculated from different steps of kinematic modelling. Our structural interpretations and modelling are integrated with new detrital zircon U-Pb geochronology to define a previously overlooked Pleistocene period of orogenic shortening and syntectonic sedimentation in the Malargüe basin. This task was possible due to the dating of three samples yielding between ∼12 and 1 Ma obtained from a 900 m deep well located in the foreland. From stratigraphic correlations, our data records an active Plio-Pleistocene wedge-top depozone coeval with retreat of the volcanism, and the emplacement of retroarc basalts. Structural modelling, together with detrital zircon U-Pb provenance data register shortening producing a foredeep to wedge-top Plio-Pleistocene transition, adjusting and completing the knowledge of the frontal fold-thrust belt and foreland basin in the southern Central Andes.</jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.7033425">https://doi.org/10.6084/m9.figshare.c.7033425</jats:ext-link> </jats:p>