ORCID Profile
0000-0002-7564-8149
Current Organisation
University of Leeds
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Computational modelling and simulation in earth sciences | Structural geology and tectonics | Geoinformatics
Publisher: Elsevier BV
Date: 12-2015
Publisher: Research Square Platform LLC
Date: 23-09-2022
DOI: 10.21203/RS.3.RS-2084887/V1
Abstract: The Permian–Triassic Mass Extinction (PTME), life’s most severe crisis1, has been attributed to intense global warming triggered by CO2 emissions from Large Igneous Province volcanism2–8. It remains unclear, however, why super-greenhouse conditions persisted for around five million years after the volcanic episode, when Earth system feedbacks should have returned temperatures to pre-extinction levels within a few hundred thousand years8. Here we use fossil occurrences and lithological indicators of climate to reconstruct spatio-temporal maps of plant productivity and biomass changes through the Permian–Triassic and undertake climate-biogeochemical modelling to investigate the unusual longevity and intensity of warming. Our reconstructions show that terrestrial vegetation collapse during the PTME, especially in tropical regions, resulted in an Earth system with low levels of organic carbon sequestration and chemical weathering, leading to limited drawdown of greenhouse gases. This led to a protracted period of extremely high surface temperatures, during which biotic recovery was delayed for millions of years. Our results support the idea that thresholds exist in the climate-carbon system beyond which warming may be lified substantially.
Publisher: Springer Science and Business Media LLC
Date: 27-05-2022
Publisher: Springer International Publishing
Date: 2021
Publisher: Springer Science and Business Media LLC
Date: 20-04-2021
DOI: 10.1038/S43247-021-00149-Z
Abstract: Plate reorganization events involve fundamental changes in lithospheric plate-motions and can influence the lithosphere-mantle system as well as both ocean and atmospheric circulation through bathymetric and topographic changes. Here, we compile published data to interpret the geological record of the Neoproterozoic Arabian-Nubian Shield and integrate this with a full-plate tectonic reconstruction. Our model reveals a plate reorganization event in the late Tonian period about 720 million years ago that changed plate-movement directions in the Mozambique Ocean. After the reorganization, Neoproterozoic India moved towards both the African cratons and Australia-Mawson and instigated the future amalgamation of central Gondwana about 200 million years later. This plate kinematic change is coeval with the breakup of the core of Rodinia between Australia-Mawson and Laurentia and Kalahari and Congo. We suggest the plate reorganization event caused the long-term shift of continents to the southern hemisphere and created a pan-northern hemisphere ocean in the Ediacaran.
Publisher: American Geophysical Union (AGU)
Date: 06-2019
DOI: 10.1029/2018TC005384
Publisher: California Digital Library (CDL)
Date: 02-03-2021
DOI: 10.31223/X56K7S
Publisher: American Association for the Advancement of Science (AAAS)
Date: 14-10-2022
Abstract: Mapping the history of atmospheric O 2 during the late Precambrian is vital for evaluating potential links to animal evolution. Ancient O 2 levels are often inferred from geochemical analyses of marine sediments, leading to the assumption that the Earth experienced a stepwise increase in atmospheric O 2 during the Neoproterozoic. However, the nature of this hypothesized oxygenation event remains unknown, with suggestions of a more dynamic O 2 history in the oceans and major uncertainty over any direct connection between the marine realm and atmospheric O 2 . Here, we present a continuous quantitative reconstruction of atmospheric O 2 over the past 1.5 billion years using an isotope mass balance approach that combines bulk geochemistry and tectonic recycling rate calculations. We predict that atmospheric O 2 levels during the Neoproterozoic oscillated between ~1 and ~50% of the present atmospheric level. We conclude that there was no simple unidirectional rise in atmospheric O 2 during the Neoproterozoic, and the first animals evolved against a backdrop of extreme O 2 variability.
Publisher: Elsevier BV
Date: 09-2017
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-9971
Abstract: Plate tectonics shapes Earth& #8217 s surface and is linked to motions within its deep interior. Cold oceanic lithosphere sinks into the mantle, and hot mantle plumes rise from the deep Earth, leading to volcanism. Volcanic eruptions over the past 320 million years have been linked to two large structures at the base of the mantle presently under Africa and the Pacific Ocean. This has led to the hypothesis that these basal mantle structures could have been stationary over geological time, in contrast to observations and models suggesting that tectonic plates, subduction zones, and mantle plumes have been mobile and that basal mantle structures are presently deforming. Here we reconstruct mantle flow from one billion years ago to the present day to show that the history of volcanism is statistically as consistent with mobile basal mantle structures as with fixed ones. In our reconstructions, cold lithosphere sank deep into the African hemisphere between 740 and 500 million years ago, and from 400 million years ago the structure beneath Africa progressively assembled, pushed by peri-Gondwana slabs, to become a coherent structure as recently as 60 million years ago. In contrast, the structure beneath the Pacific Ocean was established between 400 and 200 million years ago. These results confirm the link between basal mantle structures and surface volcanism, and they suggest that basal mantle structures are mobile, and aggregate and disperse over time, similarly to continents at Earth& #8217 s surface. This implies that the present-day shape and location of basal mantle structures may not be a suitable reference frame for the motion of tectonic plates.
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-11544
Abstract: & & The fundamental drivers of Phanerozoic climate change over geological timescales (10& #8211 s of Ma) are well recognised: degassing from the deep-earth puts carbon into the atmosphere, silicate weathering takes carbon from the atmosphere and traps it in carbonate minerals. A number of variables are purported to control or exert influence on these two mechanisms, such as the motion of tectonic plates varying the amount of degassing, the palaeogeogrpahic distribution of continents and oceans, the colonisation of land by plants and preservation of more weatherable material, such as ophiolites. We present a framework, & em& ySCION,& /em& that integrates these drivers into a single analysis, connecting solid earth with climate and biogeochemistry. Further, our framework allows us to isolate in idual drivers to determine their importance, and how it changes through time. Our model, with all drivers active, successfully reproduces the key aspects and trends of Phanerozoic temperature, to a much greater extent than previous models. We find that no single driver can explain Phanerozoic temperature with any degree of confidence, and that the most important driver varies for each geological period.& &
Publisher: Elsevier BV
Date: 02-2019
Publisher: Informa UK Limited
Date: 03-2013
Publisher: Springer Science and Business Media LLC
Date: 23-06-2022
Publisher: Geological Society of America
Date: 08-10-2018
DOI: 10.1130/G45225.1
Publisher: Springer Science and Business Media LLC
Date: 25-09-2023
Publisher: American Geophysical Union (AGU)
Date: 10-2023
DOI: 10.1029/2023GC010947
Publisher: Copernicus GmbH
Date: 07-07-2022
Abstract: Abstract. Understanding the long-term evolution of Earth's plate–mantle system is reliant on absolute plate motion models in a mantle reference frame, but such models are both difficult to construct and controversial. We present a tectonic-rules-based optimization approach to construct a plate motion model in a mantle reference frame covering the last billion years and use it as a constraint for mantle flow models. Our plate motion model results in net lithospheric rotation consistently below 0.25∘ Myr−1, in agreement with mantle flow models, while trench motions are confined to a relatively narrow range of −2 to +2 cm yr−1 since 320 Ma, during Pangea stability and dispersal. In contrast, the period from 600 to 320 Ma, nicknamed the “zippy tricentenary” here, displays twice the trench motion scatter compared to more recent times, reflecting a predominance of short and highly mobile subduction zones. Our model supports an orthoversion evolution from Rodinia to Pangea with Pangea offset approximately 90∘ eastwards relative to Rodinia – this is the opposite sense of motion compared to a previous orthoversion hypothesis based on paleomagnetic data. In our coupled plate–mantle model a broad network of basal mantle ridges forms between 1000 and 600 Ma, reflecting widely distributed subduction zones. Between 600 and 500 Ma a short-lived degree-2 basal mantle structure forms in response to a band of subduction zones confined to low latitudes, generating extensive antipodal lower mantle upwellings centred at the poles. Subsequently, the northern basal structure migrates southward and evolves into a Pacific-centred upwelling, while the southern structure is dissected by subducting slabs, disintegrating into a network of ridges between 500 and 400 Ma. From 400 to 200 Ma, a stable Pacific-centred degree-1 convective planform emerges. It lacks an antipodal counterpart due to the closure of the Iapetus and Rheic oceans between Laurussia and Gondwana as well as due to coeval subduction between Baltica and Laurentia and around Siberia, populating the mantle with slabs until 320 Ma when Pangea is assembled. A basal degree-2 structure forms subsequent to Pangea breakup, after the influence of previously subducted slabs in the African hemisphere on the lowermost mantle structure has faded away. This succession of mantle states is distinct from previously proposed mantle convection models. We show that the history of plume-related volcanism is consistent with deep plumes associated with evolving basal mantle structures. This Solid Earth Evolution Model for the last 1000 million years (SEEM1000) forms the foundation for a multitude of spatio-temporal data analysis approaches.
Publisher: Elsevier BV
Date: 02-2020
Publisher: Copernicus GmbH
Date: 26-01-2022
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-12062
Abstract: The past decade has seen the rise of fully kinematic palaeogeographic models that explicitly define the evolution of both plate boundaries and tectonic plates. Included in these models are (possible) interpretations of spreading systems in extinct ocean basins. Typically, the primary constraint on controlling these synthetic mid-ocean ridges is ensuring that at known (i.e. preserved in the geological record) subduction zones there is convergence, and that at modelled mid-ocean ridges there is ergence. The most common way this is expressed in models is through a quasi-stable triple junction. While obviously subject to large inherent uncertainties, the advantage of modelling such ocean basins is that they can provide an internally consistent model of (tectonic) ocean evolution, tied to the underlaying palaeomagnetic and palaeotectonic framework. Here we explore this inherent uncertainty in such synthetic ocean basins, by introducing the concept of & #8216 structural uncertainty& #8217 within a full-plate model. We describe structural uncertainty as the answer to the question, & #8220 how much oceanic-oceanic subduction (i.e. not preserved in the geological record) is required to balance the modelled synthetic spreading ridges?& #8221 While an initial inclination that models tending to & #8216 zero& #8217 might be best, we entertain the possibility that there is a range of & #8216 lost& #8217 subduction. To assess this hypothesis, we also interrogate whole-mantle convection models that produce self-consistent plate tectonics to determine the proportion of subduction around or adjacent to continents (representative of what might be preserved in the geological record), and subduction occurring within ocean basins (representative of what might be lost to the geological record).
Publisher: Research Square Platform LLC
Date: 22-03-2021
DOI: 10.21203/RS.3.RS-333061/V1
Abstract: The early Cenozoic exhibited profound environmental change influenced by plume magmatism, continental breakup, and opening of the North Atlantic Ocean. Global warming culminated in the transient (170 thousand year, kyr) hyperthermal event, the Palaeocene-Eocene thermal maximum (PETM) 56 million years ago (Ma). Although sedimentary methane release has been proposed as a trigger, recent studies have implicated carbon dioxide (CO 2 ) emissions from the coeval North Atlantic igneous province (NAIP). However, we calculate that volcanic outgassing from mid-ocean ridges and large igneous provinces associated with the NAIP yields only one-fifth of the carbon required to trigger the PETM. Rather, we show that volcanic sequences spanning the rift-to-drift phase of the NAIP exhibit a sudden and ∼220-kyr-long intensification of volcanism coincident with the PETM, and driven by substantial melting of the sub-continental lithospheric mantle (SCLM). Critically, the SCLM is enriched in metasomatic carbonates and is a major carbon reservoir. We propose that the coincidence of the Iceland plume and emerging asthenospheric upwelling disrupted the SCLM and caused massive mobilization of this deep carbon. Our melting models and coupled tectonic–geochemical simulations indicate the release of 4 gigatons of carbon, which is sufficient to drive PETM warming. Our model is consistent with anomalous CO 2 fluxes during continental breakup, while also reconciling the deficit of deep carbon required to explain the PETM.
Publisher: Wiley
Date: 17-10-2020
DOI: 10.1111/BRE.12520
Publisher: Geological Society of London
Date: 02-08-2021
DOI: 10.1144/JGS2021-030
Publisher: Elsevier BV
Date: 07-2013
Publisher: American Geophysical Union (AGU)
Date: 12-2016
DOI: 10.1002/2016TC004289
Publisher: Elsevier BV
Date: 03-2021
Publisher: Wiley
Date: 03-09-2020
DOI: 10.1002/GDJ3.105
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-6194
Abstract: The Permian& #8211 Triassic Mass Extinction (PTME), life& #8217 s most severe crisis1, has been attributed to intense global warming triggered by CO2& emissions from Large Igneous Province volcanism2& #8211 . It remains unclear, however, why super-greenhouse conditions persisted for around five million years after the volcanic episode, when Earth system feedbacks should have returned temperatures to pre-extinction levels within a few hundred thousand years8. Here we reconstruct spatio-temporal maps of plant productivity through the Permian& #8211 Triassic and undertake climate-biogeochemical modelling to investigate the unusual longevity and intensity of warming. Our reconstructions& show that terrestrial vegetation collapse during the PTME, especially in tropical regions, resulted in an Earth system with low levels of organic carbon sequestration and chemical weathering, leading to limited drawdown of greenhouse gases& and& rotracted period of extremely high surface temperatures.
Publisher: Springer Science and Business Media LLC
Date: 30-03-2022
DOI: 10.1038/S41586-022-04538-Y
Abstract: Plate tectonics shapes Earth's surface, and is linked to motions within its deep interior
Publisher: California Digital Library (CDL)
Date: 31-01-2022
DOI: 10.31223/X52S4G
Abstract: Recent progress in plate tectonic reconstructions has seen models move beyond the classical idea of continental drift by attempting to reconstruct the full evolving configuration of tectonic plates and plate boundaries. A particular problem for the Neoproterozoic and Cambrian is that many existing interpretations of geological and palaeomagnetic data have remained disconnected from younger, better-constrained periods in Earth history. An important test of deep time reconstructions is therefore to demonstrate the continuous kinematic viability of tectonic motions across multiple supercontinent cycles. We present, for the first time, a continuous full-plate model spanning 1 Ga to the present-day, that includes a revised and improved model for the Neoproterozoic–Cambrian (1000–520 Ma) that connects with models of the Phanerozoic, thereby opening up pre-Gondwana times for quantitative analysis and further regional refinements. In this contribution, we first summarise methodological approaches to full-plate modelling and review the existing full-plate models in order to select appropriate models that produce a single continuous model. Our model is presented in a palaeomagnetic reference frame, with a newly-derived apparent polar wander path for Gondwana from 540 to 320 Ma, and a global apparent polar wander path from 320 to 0 Ma. We stress, though while we have used palaeomagnetic data when available, the model is also geologically constrained, based on preserved data from past-plate boundaries. This study is intended as a first step in the direction of a detailed and self-consistent tectonic reconstruction for the last billion years of Earth history, and our model files are released to facilitate community development.
Publisher: Frontiers Media SA
Date: 27-08-2020
Publisher: Copernicus GmbH
Date: 26-01-2022
DOI: 10.5194/SE-2021-154
Abstract: Abstract. Understanding the long-term evolution of Earth's plate-mantle system is reliant on absolute plate motion models in a mantle reference frame, but such models are both difficult to construct and controversial. We present a tectonic rules-based optimisation approach to construct a plate motion model in a mantle reference frame covering the last billion years and use it as a surface boundary condition for mantle flow models. Our plate motion model results in lithospheric net rotation consistently below 0.25°/Myr, in agreement with mantle flow models, while trench motions are confined to a relatively narrow range of −2/+2 cm/yr since 320 Ma, during Pangea stability and dispersal. In contrast, the period from 600 Ma to 320 Ma, nicknamed here the "zippy tricentenary", displays twice the trench motion scatter compared to more recent times, reflecting a predominance of short and highly mobile subduction zones. Our model supports an orthoversion evolution from Rodinia to Pangea with Pangea offset approximately 90° eastwards relative to Rodinia—this is the opposite sense of motion compared to a previous orthoversion hypothesis based on paleomagnetic data. In our coupled plate-mantle model a broad network of basal mantle ridges forms between 1000 and 600 Ma, reflecting widely distributed subduction zones. Between 600 and 500 Ma a short-lived degree-2 basal mantle structure forms in response to a band of subduction zones confined to low-latitudes, generating extensive antipodal lower mantle upwellings centred at the poles. Subsequently the northern basal structure migrates southward and morphs into a Pacific-centred upwelling while the southern structure is dissected by subducting slabs and disintegrates into a network of ridges between 500 and 400 Ma. From 400 to 200 Ma, a stable Pacific-centred degree-1 convective planform emerges, lacking an antipodal counterpart due to the closure of the Iapetus and Rheic oceans between Laurussia and Gondwana as well as coeval subduction between Baltica and Laurentia and around Siberia, populating the mantle with slabs until 320 Ma when Pangea is assembled. A basal degree-2 structure forms subsequent to Pangea breakup, after the influence of previously subducted slabs in the African hemisphere on the lowermost mantle has faded away. This succession of mantle states is distinct from previously proposed mantle convection models. This Solid Earth Evolution Model for the last 1000 million years (SEEM1000) forms the foundation for a multitude of spatio-temporal data analysis approaches.
Publisher: Springer Science and Business Media LLC
Date: 20-10-2023
Publisher: Authorea, Inc.
Date: 29-09-2023
Publisher: Springer Science and Business Media LLC
Date: 25-05-2022
Publisher: American Geophysical Union (AGU)
Date: 04-2020
DOI: 10.1029/2019GC008869
Publisher: Elsevier BV
Date: 10-2017
Publisher: Springer Science and Business Media LLC
Date: 23-08-2021
Publisher: Research Square Platform LLC
Date: 08-12-2021
DOI: 10.21203/RS.3.RS-986686/V1
Abstract: Diamonds are erupted at Earth’s surface in volatile-rich magmas called kimberlites 1,2,3 . These enigmatic magmas, originating from depths exceeding 150 kilometres in Earth’s mantle 1 , occur in stable cratons and in pulses broadly synchronous with supercontinent cyclicity 4 . Whether their mobilization is driven by mantle plumes 5 or mechanical weakening of cratonic lithosphere 4,6 remains unclear. Here we show that most kimberlites spanning the past billion years erupted approximately 25 million years after the onset of continental fragmentation, suggesting an association with rifting processes. Our dynamic models show that physically steep lithosphere-asthenosphere boundaries formed during terminal rifting (necking) generate convective instabilities in the asthenosphere that slowly migrate many hundreds of kilometres inboard of the rift, causing destabilization of cratonic mantle keel tens of kilometres thick. Displaced lithosphere is replaced by hot, upwelling asthenosphere in the return flow, causing partial melting of carbonated mantle and variable assimilation of lithospheric material. The resulting small-volume kimberlite magmas ascend rapidly and adiabatically, exsolving amounts of carbon dioxide (CO 2 ) that are consistent with independent constraints 7 . Our model reconciles diagnostic kimberlite features including association with cratons and geochemical characteristics that implicate a common asthenospheric mantle source contaminated by cratonic lithosphere 8 . Together, these results provide a quantitative and mechanistic link between kimberlite episodicity and supercontinent cycles via progressive disruption of cratonic keels.
Publisher: Springer Science and Business Media LLC
Date: 26-07-2023
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2023
End Date: 12-2025
Amount: $357,299.00
Funder: Australian Research Council
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