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The timing and duration of silicic magmatism at relatively small volcanic centres in the geological record remain poorly constrained but are vital for understanding the temporal evolution of magmatic provinces. The Palaeogene Central Arran Igneous Complex (CAIC), and the nearby North Arran Granite, show spatial and temporal relationships between silicic intrusions and intra-caldera volcanic deposits. High-precision Usingle bondPb zircon geochronology, integrated with detailed field observations, allows a timeline of silicic magmatic activity on Arran to be constrained. Silicic magmatism in north and central Arran occurred as a very short-lived (∼0.5 Ma) ‘pulse’ during the protracted (>8 Ma) evolution of the British Palaeogene Igneous Province (BPIP). Evolution of the CAIC volcano from caldera collapse to eruption of the youngest preserved unit (including several phases of eruption punctuated by quiescent periods of land surface erosion and deposition of sediments) took no more than 185 ka. Silicic magmatism at the complex (volcanism followed by intrusion of granites) lasted no more than 330 ka, with the North Arran Granite was emplaced shortly prior to the CAIC. This evidence of a short magmatic pulse accompanied by drastic land-surface changes has major implications for our understanding of localised silicic magmatism in other igneous provinces, both in the geological record and the present day.

The hydrocarbon seepage chronology during deglaciation across the formerly glaciated Barents Sea was established using uranium-thorium (U–Th) dating of seep carbonates. Seep carbonates were sampled with remotely operated vehicles (ROV) from the seafloor at three active hydrocarbon seeps (water depth 156–383 m), located in the north-west (Storfjordrenna), north-central (Storbanken High), and south-west (Loppa High) Barents Sea. Overall, the U–Th dates range from 13.5 to 1.2 thousand years (ka) before present, indicating episodic seep carbonate formation since the late Pleistocene throughout the Holocene. The new U–Th dates indicate protracted post-glacial gas seepage, congruent with previously published seep carbonate ages from the south-west Barents Sea. Gas hydrate dissociation and associated seep carbonate formation occurred at Storfjordrenna between ≈6 and 1.2 ka, and around 13.5 and 6 ka at Storbanken. Early and late Holocene seep carbonate ages from Loppa High support post-glacial seismic activity as potential seepage trigger mechanism.

The Llangynog Inlier of south Wales contains an assemblage of Ediacaran macrofossils from a shallow-marine environment, including discoidal morphs of Aspidella and rare examples of Hiemalora, Palaeopascichnus and Yelovichnus. These are taxa found at other sites in the Avalonian microcontinent (e.g. Charnwood Forest and eastern Newfoundland) and in the younger White Sea Ediacaran assemblages. As the Charnwood fossils reflect a deep-water environment, and no macrofossils have been found in the Ediacaran rocks of the Long Mynd, the fossils of the Llangynog Inlier represent a unique glimpse of shallow-marine life in southern Britain (East Avalonia). However, the lack of absolute age constraints has hampered direct comparison with other assemblages. Here, we report in situ zircon and rutile U–Pb dates from a rhyolitic ash-flow layer of the Coed Cochion Volcaniclastic Member, Llangynog Inlier, which constrains the age of the fossiliferous strata. A weighted mean single grain zircon isotope dilution thermal ionization mass spectrometry U–Pb age of 564.09 ± 0.70 Ma is interpreted as the rhyolite's crystallization age. This age is consistent with in situ laser ablation inductively coupled plasma mass spectrometry zircon and rutile U–Pb dating. The Llangynog age temporally correlates these fossils to dated horizons within East Avalonia at the Beacon Hill Formation, Charnwood (565.22 ± 0.89 Ma) and the Stretton Shale Formation, Long Mynd (566.6 ± 2.9 Ma). Correlations to West Avalonia include the time-equivalent Fermeuse Formation, St John's Group, eastern Newfoundland (564.13 ± 0.65 Ma). The data presented here establish the biota of the Llangynog Inlier as a lateral equivalent to the similarly shallow-marine, tidally influenced ecosystem of the upper Fermeuse Formation. Intra-terrane depositional environmental variability also affects what is preserved in Avalonian fossil sites. Further, time-constrained geochemical data reinforce the Llangynog Inlier's classification within

Enriched mid-ocean ridge basalts (E-MORB) commonly erupt at mid-ocean ridges (MOR) and seamounts, but their relationship to “depleted” MORB (D-MORB) and the processes controlling their magmatic evolution at MORs are not fully understood, hence raising more general questions about magma generation in the mantle. We here explore this conundrum through an investigation of the Masirah ophiolite (southeast Oman), a near-unique “true” MOR ophiolite. Unlike most (e.g., Tethyan) ophiolites, it was not affected by subduction and is therefore potentially able to provide valuable geological insights into the magmatic evolution of a full section of oceanic crust. Previous work has shown that the igneous crust at Masirah was thin (1.5–2.0 km) and constructed from both D- and E-MORB magmas, concluding that it formed at a slow-spreading ridge at ∼150 Ma followed by an episode of “Nb-enriched” magmatism with trace-element enrichments exceeding E-MORB during intraplate rifting ∼20 Ma later. We reinvestigate the geology of Masirah and present new field observations, geochemical data and high-precision U-Pb ages to constrain the magmatic history of seafloor spreading and off-axis magmatism. We found that D-MORB and E-MORB magmatism at Masirah was synchronous and overlapped in both composition and time with the Nb-enriched magmatism (no older than 135 Ma). Both types of magmatism were therefore integral in the formation of the Masirah ocean crust. The relationship between D-MORB and E-MORB magmatism described here may be applicable to modern MORs more broadly, but is especially prominent at Masirah due to reduced magmatism and hence a weaker crustal filter.

Drilling for the International Continental Scientific Drilling Program (ICDP) Early Jurassic Earth System and Timescale project (JET) was undertaken between October 2020 and January 2021. The drill site is situated in a small-scale synformal basin of the latest Triassic to Early Jurassic age that formed above the major Permian-Triassic half-graben system of the Cheshire Basin. The borehole is located to recover an expanded and complete succession to complement the legacy core from the Llanbedr (Mochras Farm) borehole drilled through 1967-1969 on the edge of the Cardigan Bay Basin, North Wales. The overall aim of the project is to construct an astronomically calibrated integrated timescale for the Early Jurassic and to provide insights into the operation of the Early Jurassic Earth system. Core of Quaternary age cover and Early Jurassic mudstone was obtained from two shallow partially cored geotechnical holes (Prees 2A to 32.2g¯m below surface (mg¯b.s.) and Prees 2B to 37.0g¯mg¯b.s.) together with Early Jurassic and Late Triassic mudstone from the principal hole, Prees 2C, which was cored from 32.92 to 651.32g¯m (corrected core depth scale). Core recovery was 99.7g¯% for Prees 2C. The ages of the recovered stratigraphy range from the Late Triassic (probably Rhaetian) to the Early Jurassic, Early Pliensbachian (Ibex Ammonoid Chronozone). All ammonoid chronozones have been identified for the drilled Early Jurassic strata. The full lithological succession comprises the Branscombe Mudstone and Blue Anchor formations of the Mercia Mudstone Group, the Westbury and Lilstock formations of the Penarth Group, and the Redcar Mudstone Formation of the Lias Group. A distinct interval of siltstone is recognized within the Late Sinemurian of the Redcar Mudstone Formation, and the name "Prees Siltstone Member"is proposed. Depositional environments range from playa lake in the Late Triassic to distal offshore marine in the Early Jurassic. Initial datasets compiled from the core in

Studies of oceanic crust, which covers a large proportion of the Earth's surface, have provided significant insight into the dynamics of crustal accretion processes at mid-ocean ridges. It is now recognized that the nature of oceanic crust varies fundamentally as a function of spreading rate. Ocean Drilling Program (ODP) Hole 1256D (eastern Pacific Ocean) was drilled into the crust formed at a superfast spreading rate, and hence represents a crustal end member. Drilling recovered a section through lava and sheeted dykes and into the plutonic sequence, the study of which has yielded abundant insight into magmatic and hydrothermal processes operating at high spreading rates. Here, we present zircon U-Pb dates for Hole 1256D, which constrain the age of the section, as well as the duration of crustal accretion. We find that the main pulse of zircon crystallization within plutonic rocks occurred at 15.19 Ma, consistent with magnetic anomalies, and lasted tens of thousands of years. During this episode, the main plutonic body intruded, and partial melts of the base of the sheeted dykes crystallized. One sample appears to postdate this episode by up to 0.25 Myr, and may be an off-axis intrusion. Overall, the duration of crustal accretion was tens to several hundreds of thousands of years, similar to that found at the fast-spreading East Pacific Rise and the slow-spreading Mid-Atlantic Ridge. This indicates that crustal accretion along slow- to superfast-spreading ridges occurs over similar time scales, with substantially longer periods of accretion occurring at ultraslow-spreading ridges characterized by thick lithosphere.

Drilling for the International Continental Scientific Drilling Program (ICDP) Early Jurassic Earth System and Timescale project (JET) was undertaken between October 2020 and January 2021. The drill site is situated in a small-scale synformal basin of the latest Triassic to Early Jurassic age that formed above the major Permian-Triassic half-graben system of the Cheshire Basin. The borehole is located to recover an expanded and complete succession to complement the legacy core from the Llanbedr (Mochras Farm) borehole drilled through 1967-1969 on the edge of the Cardigan Bay Basin, North Wales. The overall aim of the project is to construct an astronomically calibrated integrated timescale for the Early Jurassic and to provide insights into the operation of the Early Jurassic Earth system. Core of Quaternary age cover and Early Jurassic mudstone was obtained from two shallow partially cored geotechnical holes (Prees 2A to 32.2g¯m below surface (mg¯b.s.) and Prees 2B to 37.0g¯mg¯b.s.) together with Early Jurassic and Late Triassic mudstone from the principal hole, Prees 2C, which was cored from 32.92 to 651.32g¯m (corrected core depth scale). Core recovery was 99.7g¯% for Prees 2C. The ages of the recovered stratigraphy range from the Late Triassic (probably Rhaetian) to the Early Jurassic, Early Pliensbachian (Ibex Ammonoid Chronozone). All ammonoid chronozones have been identified for the drilled Early Jurassic strata. The full lithological succession comprises the Branscombe Mudstone and Blue Anchor formations of the Mercia Mudstone Group, the Westbury and Lilstock formations of the Penarth Group, and the Redcar Mudstone Formation of the Lias Group. A distinct interval of siltstone is recognized within the Late Sinemurian of the Redcar Mudstone Formation, and the name "Prees Siltstone Member"is proposed. Depositional environments range from playa lake in the Late Triassic to distal offshore marine in the Early Jurassic. Initial datasets compiled from the core in

The rate of movement of Earth’s solid shell relative to its spin axis, or true polar wander, depends on variations in mantle convection and viscosity. We report paleomagnetic and geochronologic data from South China that constrain the rate of rapid true polar wander (>5° per million years) between 832 million years and 821 million years ago. Analysis of the paleomagnetic database demonstrates secular change of true polar wander related to mantle cooling and thermal structure across supercontinent cycles. True polar wander rates are relatively muted with a partially insulated mantle during supercontinent assembly and accelerate as mantle thermal mixing reestablishes with supercontinent breakup. Decreasing true polar wander rate through the Neoproterozoic was succeeded by overall smaller variations in the Phanerozoic. We propose that Neoproterozoic extensive plate tectonic activities enhanced mantle cooling, giving rise to a reduction in mantle convective forcing, an increase in mantle viscosity, and a decrease in true polar wander rates into the Phanerozoic.

The rise of complex macroscopic life occurred during the Ediacaran Period, an interval that witnessed large-scale disturbances to biogeochemical systems. The current Ediacaran chronostratigraphic framework is of insufficient resolution to provide robust global correlation schemes or test hypotheses for the role of biogeochemical cycling in the evolution of complex life. Here, we present new radio-isotopic dates from Ediacaran strata that directly constrain key fossil assemblages and large-magnitude carbon cycle perturbations. These new dates and integrated global correlations demonstrate that late Ediacaran strata of South China are time transgressive and that the 575- to 550-Ma interval is marked by two large negative carbon isotope excursions: the Shuram and a younger one that ended ca. 550 Ma ago. These data calibrate the tempo of Ediacaran evolution characterized by intervals of tens of millions of years of increasing ecosystem complexity, interrupted by biological turnovers that coincide with large perturbations to the carbon cycle.

The base of the Priabonian Stage is one of two stage boundaries in the Paleogene that remains to be formalized. The Alano section (NE Italy) was elected by consensus as a suitable candidate for the base of the Priabonian during the Priabonian Working Group meeting held in Alano di Piave in June 2012. Further detailed research on the section is now followed by a formal proposal, which identifies the base of a prominent crystal tuff layer, the Tiziano bed, at meter 63.57 of the Alano section, as a suitable candidate for the Priabonian Stage. The choice of the Tiziano bed is appropriate from the historical point of view and several bio-magnetostratigraphic events are available to approximate this chronostratigraphic boundary and guarantee a high degree of correlatability over wide geographic areas. Events which approximate the base of the Priabonian Stage in the Alano section are the successive extinction of large acarininids and Morozovelloides (planktonic foraminifera), the Base of common and continuous Cribrocentrum erbae and the Top of Chiasmolithus grandis (nannofossils), as well as the Base of Subchron C17n.2n and the Base of Chron C17n (magnetostratigraphy). Cyclostratigraphic analysis of the Bartonian-Priabonian transition of the Alano section as well as radioisotopic data of the Tiziano tuff layer provide an absolute age (37.710 – 37.762 Ma, respectively) of this bed and, consequently, of the base of the Priabonian Stage.

The Conception and St. John’s Groups of southeastern Newfoundland contain some of the oldest known fossils of the Ediacaran macrobiota. The Mistaken Point Ecological Reserve UNESCO World Heritage Site is an internationally recognized locality for such fossils and hosts early evidence for both total group metazoan body fossils and metazoan-style locomotion. The Mistaken Point Ecological Reserve sedimentary succession includes ∼1500 m of fossil-bearing strata containing numerous dateable volcanogenic horizons, and therefore offers a crucial window into the rise and diversification of early animals. Here we present six stratigraphically coherent radioisotopic ages derived from zircons from volcanic tuffites of the Conception and St. John’s Groups at Mistaken Point Ecological Reserve. The oldest architecturally complex macrofossils, from the upper Drook Formation, have an age of 574.17 ± 0.66 Ma (including tracer calibration and decay constant uncertainties). The youngest rangeomorph fossils from Mistaken Point Ecological Reserve, in the Fermeuse Formation, have a maximum age of 564.13 ± 0.65 Ma. Fossils of the famous “E” Surface are confirmed to be 565.00 ± 0.64 Ma, while exceptionally preserved specimens on the “Brasier” Surface in the Briscal Formation are dated at 567.63 ± 0.66 Ma. We use our new ages to construct an age-depth model for the sedimentary succession, constrain sedimentary accumulation rates, and convert stratigraphic fossil ranges into the time domain to facilitate integration with time-calibrated data from other successions. Combining this age model with compiled stratigraphic ranges for all named macrofossils within the Mistaken Point Ecological Reserve succession, spanning 76 discrete fossil-bearing horizons, enables recognition and interrogation of potential evolutionary signals. Peak taxonomic diversity is recognized within the Mistaken Point and Trepassey Formations, and uniterminal rangeomorphs with undisplayed branching architecture appear seve