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<jats:p>Rift basin evolution is often influenced by the reactivation of pre-existing structures, a response that is partly controlled by the angular relationship of fault strike and subsequent extension/compression axes. In the Celtic Sea basins, offshore Ireland, Caledonian and Variscan structures form a heterogeneous basement for rifting in the Triassic-Jurassic and Cretaceous, and for later Pyrenean inversion in the Paleogene. Using 2D and 3D seismic reflection data, we evaluate the impact of a range of pre-existing structures on the style of deformation within basin margin and basin axis settings. Earlier Triassic-Jurassic rift phases arising from NW-SE extension, exploited NNE-SSW, NE-SW and ENE-WSW trending basement structures. By contrast, Cretaceous rifting, with a dominant N-S extension direction, generated newly formed, approximately E-W trending, normal faults which interacted with pre-existing faults that were only reactivated when they were at &gt; 45° to the extension direction. During basin inversion arising from N-S compression, orthogonal extensional faults and highly oblique basement structures were reactivated as reverse and strike/oblique-slip faults, and together interacted with newly formed strike-slip faults. Combining constraints from multiple deformation phases this study highlights the reactivation response of variably oriented faults to changing extension and compression vectors, and the associated changes in fault behaviour and mode of fault formation.</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.6168279">https://doi.org/10.6084/m9.figshare.c.6168279</jats:ext-link> </jats:p>

<jats:p> Late Ordovician–Early Silurian intermediate igneous rocks have been detected in the Dunhuang Block, NW China. These igneous rocks help to better constrain the tectonic evolution of the Dunhuang Block and even the southern Central Asian Orogenic Belt during the early Paleozoic. In this contribution, zircon U–Pb dating, whole-rock geochemistry, and zircon Hf isotope analyses are conducted on the early Paleozoic gneissic diorites from the Sanweishan and northern Huangshuihou areas in the Dunhuang Block. Zircon U–Pb geochronology demonstrated that the emplacement ages of the gneissic dioritic rocks were ca. 443–440 Ma. The dioritic rocks show varying SiO <jats:sub>2</jats:sub> (48.1–63.1 wt.%) and MgO (1.87–3.52 wt.%) contents with high Mg <jats:sup>#</jats:sup> (46–52) values, and negative Eu anomalies (Eu/Eu* = 0.62–0.94). Zircons in the gneissic diorites from the northern Huangshuigou and Sanweishan areas yield variable <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ε</mml:mi> </mml:math> </jats:inline-formula> <jats:sub>Hf</jats:sub> (t) values of −4.4 to +10.4 and –8.6 to –6.2, respectively, coupled with low Rb/Sr (0.04–0.34), Rb/Ba (0.06–0.31), and Al <jats:sub>2</jats:sub> O <jats:sub>3</jats:sub> /(MgO + FeO <jats:sup>T</jats:sup> ) (0.72–1.47) ratios, indicating that the they were predominately generated by disequilibrium melting of the juvenile crust and mixed with ancient crustal and minor mantle melts. In conjunction with previously published data, we propose that the early Paleozoic gneissic dioritic rocks were formed in a continental margin arc setting related to the southward subduction of the Paleo-Asian Ocean. Additionally, our findings point out that the Dunhuang Block was generally modified and reactivated by the Paleozoic orogenic events related to the evolution of the Paleo-Asian Ocean, resulting in extensive Paleozoic magmatism–metamorphism activities in the whole Dunhuang area. </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.6174601">https://doi.org/10.6084/m9.figshare.c.6174601</jats:ext-link> </jats:p>

<jats:p> The Palaeozoic radiodonts are important for understanding the evolution and ecology of early euarthropods. However, complete radiodont fossils are very rare, despite their central roles in understanding radiodont palaeobiology. Here we describe <jats:italic>Innovatiocaris maotianshanensis</jats:italic> gen. et sp. nov. in detail based on an iconic complete radiodont specimen from the early Cambrian Chengjiang Lagerstätte of China. The head of <jats:italic>I</jats:italic> . <jats:italic>maotianshanensis</jats:italic> has a pair of stalked eyes, an ovate dorsal sclerite, a pair of frontal appendages composed of 11 distal articulated podomeres bearing spiky endites with only anterior auxiliary spines, and a putative triradial oral cone. The body possesses six anterior pairs of small differentiated neck flaps and ten posterior pairs of trunk flaps, with soft tissues including alimentary canal and musculature preserved. The tail includes a tail fan comprising three pairs of lateral blades and a pair of very long furcae. Another two new species, <jats:italic>Innovatiocaris</jats:italic> ? sp. and <jats:italic>I</jats:italic> .? <jats:italic>multispiniformis</jats:italic> sp. nov., are established based on the frontal appendages with different numbers of anterior auxiliary spines and are tentatively assigned to <jats:italic>Innovatiocaris</jats:italic> . Phylogenetic analysis retrieves <jats:italic>Innovatiocaris</jats:italic> as either a basal member of Hurdiidae or early-branching species of the non-hurdiid clade. Thus, <jats:italic>Innovatiocaris</jats:italic> provides new insights into the radiodont phylogeny and illuminates the early diversification of Radiodonta. </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> Supplementary figures, phylogenetic data matrix, and a character list for phylogenetic analysis are available 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.6179300">https://doi.org/10.6084/m9.figshare.c.6179300</jats:ext-link> </jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Advances in the Cambrian Explosion 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/advances-in-the-cambrian-explosion">https://www.lyellcollection.org/topic/collections/advances-in-the-cambrian-explosion</jats:ext-link> </jats:p>

<jats:p>Sills are important components of magmatic plumbing systems due to their role as storage features of magma. Previous studies have indirectly investigated sill propagation and architecture by using laboratory experiments, remote sensing, modelling and theory. These studies, however, often struggle to include the complexity of natural systems, which often includes strong interplay between host and intruder. To elevate the importance of host rock and magma interaction, we present the results from a study of combined UAV- and outcrop datasets from world-class 1.3 km long, 30 m high 3D exposure of a 12 m thick alkaline trachybasalt sill in Mussentuchit Wash, San Rafael Swell, Utah. The sill intruded into Jurassic, dominantly sandy, sedimentary rocks. Results of this study shows that the propagation of the Mussentuchit Wash Sill features both fracture-driven- and complex non-brittle fluid interaction emplacement, which are strongly influenced by local sedimentology and presence of porewater. Segregated melt emplaced progressively within the sill during emplacement is used to document the evolution of sill inflation. The fracture-driven propagation is initiated along sedimentary discontinuities through hydrofracturing, while the non-brittle fluid interaction is caused by the presence of local porewater within the sedimentary host rocks. This suggests that local lithology may exert strong control on the architecture and morphology of sills in sedimentary basins.</jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> The 3D model of the Mussentuchit Wash Sill (e.g. Figure 4) will be published on V3Geo.com (currently open-access database for 3D models) when the manuscript is published. Uninterpreted images of the sill will be published on figshare and are included as DR1. </jats:p>

<jats:p> Numerical simulations and theoretical analyses predict that forearc ophiolites probably record the end of subduction followed by re-initiation. We report here the results of a field study and new geochronological data that enable identification of the Kermanshah forearc basin, SW Iran. This basin is filled with two terrestrial volcaniclastic successions separated by an Upper Cretaceous reef facies limestone. Early Late Cretaceous ocean island basalts, early Eocene incompatible element-enriched mid-ocean ridge basalts/normal-type mid-ocean ridge basalts and late Eocene arc basalts of the basin indicate that Neotethyan subduction ended during the early Late Cretaceous and then re-initiated during the late Eocene. We suggest that the Neotethyan Ocean between the Iranian and Arabian continents consisted of leading and trailing oceanic plates separated by a mid-ocean ridge (MOR). Subduction of the leading plate generated the Jurassic–Early Cretaceous Sanandaj–Sirjan arc, which was ended by MOR–trench collision. The Zagros late Early Cretaceous forearc ophiolites represent the youngest/hottest segments of the leading plate emplaced during the MOR–trench collision. Subsequently, subduction of the MOR generated the forearc basin and basalts with diverse geochemistry. After <jats:italic>c.</jats:italic> 60 myr, the cooled trailing plate started to subduct, generating the late Eocene arc basalts. This model has significant implications for investigating and understanding other fossil subduction zones elsewhere in the world. </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> Supplementary material is available 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.6086586">https://doi.org/10.6084/m9.figshare.c.6086586</jats:ext-link> </jats:p>