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  • 1
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    Early India-Australia spreading history revealed by newly detected Mesozoic magnetic anomalies in the Perth Abyssal Plain (2013)
    Wiley
    Details
    Publication Date: 2013-06-12
    Description: [1]  The seafloor within the Perth Abyssal Plain (PAP), offshore Western Australia, is the only section of crust that directly records the early spreading history between India and Australia during the Mesozoic breakup of Gondwana. However, this early spreading has been poorly constrained due to an absence of data, including marine magnetic anomalies and data constraining the crustal nature of key tectonic features. Here, we present new magnetic anomaly data from the PAP that shows that the crust in the western part of the basin was part of the Indian Plate – the conjugate flank to the oceanic crust immediately offshore the Perth margin, Australia. We identify a sequence of M2 and older anomalies in the west PAP within crust that initially moved with the Indian Plate, formed at intermediate half-spreading rates (35 mm/yr) consistent with the conjugate sequence on the Australian Plate. More speculatively, we reinterpret the youngest anomalies in the east PAP, finding that the M0-age crust initially formed on the Indian Plate was transferred to the Australian Plate by a westward jump or propagation of the spreading ridge shortly after M0 time. Samples dredged from the Gulden Draak and Batavia Knolls (at the western edge of the PAP) reveal that these bathymetric features are continental fragments rather than igneous plateaus related to Broken Ridge. These microcontinents rifted away from Australia with Greater India during initial breakup at ~130 Ma, then rifted from India following the cessation of spreading in the PAP (~101-103 Ma).
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Abrupt plate accelerations shape rifted continental margins (2016)
    Springer Nature
    In: Nature
    Details
    Publication Date: 2016-08-11
    Description: Abrupt plate accelerations shape rifted continental margins Nature 536, 7615 (2016). doi:10.1038/nature18319 Authors: Sascha Brune, Simon E. Williams, Nathaniel P. Butterworth & R. Dietmar Müller Rifted margins are formed by persistent stretching of continental lithosphere until breakup is achieved. It is well known that strain-rate-dependent processes control rift evolution, yet quantified extension histories of Earth’s major passive margins have become available only recently. Here we investigate rift kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions. We find that rifted margins feature an initial, slow rift phase (less than ten millimetres per year, full rate) and that an abrupt increase of plate divergence introduces a fast rift phase. Plate acceleration takes place before continental rupture and considerable margin area is created during each phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. The extension models suggest that the two-phase velocity behaviour is caused by a rift-intrinsic strength–velocity feedback, which can be robustly inferred for diverse lithosphere configurations and rheologies. Our results explain differences between proximal and distal margin areas and demonstrate that abrupt plate acceleration during continental rifting is controlled by the nonlinear decay of the resistive rift strength force. This mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes, offering new insights into the balance of plate driving forces through time.
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 3
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    A rapid burst in hotspot motion through the interaction of tectonics and deep mantle flow (2016)
    Springer Nature
    In: Nature
    Details
    Publication Date: 2016-05-12
    Description: A rapid burst in hotspot motion through the interaction of tectonics and deep mantle flow Nature 533, 7602 (2016). doi:10.1038/nature17422 Authors: Rakib Hassan, R. Dietmar Müller, Michael Gurnis, Simon E. Williams & Nicolas Flament Volcanic hotspot tracks featuring linear progressions in the age of volcanism are typical surface expressions of plate tectonic movement on top of narrow plumes of hot material within Earth’s mantle. Seismic imaging reveals that these plumes can be of deep origin—probably rooted on thermochemical structures in the lower mantle. Although palaeomagnetic and radiometric age data suggest that mantle flow can advect plume conduits laterally, the flow dynamics underlying the formation of the sharp bend occurring only in the Hawaiian–Emperor hotspot track in the Pacific Ocean remains enigmatic. Here we present palaeogeographically constrained numerical models of thermochemical convection and demonstrate that flow in the deep lower mantle under the north Pacific was anomalously vigorous between 100 million years ago and 50 million years ago as a consequence of long-lasting subduction systems, unlike those in the south Pacific. These models show a sharp bend in the Hawaiian–Emperor hotspot track arising from the interplay of plume tilt and the lateral advection of plume sources. The different trajectories of the Hawaiian and Louisville hotspot tracks arise from asymmetric deformation of thermochemical structures under the Pacific between 100 million years ago and 50 million years ago. This asymmetric deformation waned just before the Hawaiian–Emperor bend developed, owing to flow in the deepest lower mantle associated with slab descent in the north and south Pacific.
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 4
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    Origin of Long‐Wavelength Magnetic Anomalies at Subduction Zones (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Most subduction zones have associated long‐wavelength anomalies in the lithospheric magnetic field observed at satellite altitude. We model the 13 subduction zones defined by seismicity and seismic tomography using vertically integrated magnetisations (VIM) that are either increasing, level, or decreasing away from the trench. These mimic end members of a magnetised mantle wedge, a uniform layer, and a magnetised dipping lithospheric slab. They are added to a global model of VIM based on continental and oceanic geology. We find the dipping slab places the anomaly too close to the trench while the other two fit the data equally well, and use the level model in the main part of the study. Anomalies at the Sunda, Aleutians, Cascadia, Central American and Kamchatka‐Japan zones are well modelled by uniform magnetisation of differing susceptibilities and spatial extents. We show the South American anomaly is weak because the magnetisation lies mainly in the null space that produces no external potential magnetic field. There is no anomaly associated with the Ryukyu system, possibly because the present subduction started too recently for magnetisation to have formed. The magnetic anomaly stretching down the Baja California peninsula is not present in the prediction because there is no seismicity on which to base a slab geometry, but recent tomography suggests a fossil slab there and we propose historic subduction as the origin of the Baja magnetic anomaly. Finally, we discuss the mineralogical origins of the magnetisation and favour serpentinisation of the region above the subducted plate.
    Print ISSN: 2169-9313
    Electronic ISSN: 2169-9356
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    A Global Plate Model Including Lithospheric Deformation Along Major Rifts and Orogens Since the Triassic (2019)
    Wiley
    In: Tectonics
    Details
    Publication Date: 2019
    Description: Abstract Global deep‐time plate motion models have traditionally followed a classical rigid plate approach, even though plate deformation is known to be significant. Here we present a global Mesozoic–Cenozoic deforming plate motion model that captures the progressive extension of all continental margins since the initiation of rifting within Pangea at ~240 Ma. The model also includes major failed continental rifts and compressional deformation along collision zones. The outlines and timing of regional deformation episodes are reconstructed from a wealth of published regional tectonic models and associated geological and geophysical data. We reconstruct absolute plate motions in a mantle reference frame with a joint global inversion using hot spot tracks for the last 80 million years and minimizing global trench migration velocities and net lithospheric rotation. In our optimized model, net rotation is consistently below 0.2°/Myr, and trench migration scatter is substantially reduced. Distributed plate deformation reaches a Mesozoic peak of 30 × 106 km2 in the Late Jurassic (~160–155 Ma), driven by a vast network of rift systems. After a mid‐Cretaceous drop in deformation, it reaches a high of 48 x 106 km2 in the Late Eocene (~35 Ma), driven by the progressive growth of plate collisions and the formation of new rift systems. About a third of the continental crustal area has been deformed since 240 Ma, partitioned roughly into 65% extension and 35% compression. This community plate model provides a framework for building detailed regional deforming plate networks and form a constraint for models of basin evolution and the plate‐mantle system.
    Print ISSN: 0278-7407
    Electronic ISSN: 1944-9194
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Constraining absolute plate motions since the Triassic (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract The absolute motion of tectonic plates since Pangea can be derived from observations of hotspot trails, paleomagnetism or seismic tomography. However, fitting observations is typically carried out in isolation without consideration for the fit to unused data or whether the resulting plate motions are geodynamically plausible. Through the joint evaluation of global hotspot track observations (for times 〈 80 Ma), first‐order estimates of net lithospheric rotation (NLR), and parameter estimation for paleo‐trench migration (TM), we present a suite of geodynamically consistent, data‐optimised global absolute reference frames from 220 Ma to the present. Each absolute plate motion (APM) model was evaluated against six published APM models, together incorporating the full range of primary data constraints. Model performance for published and new models was quantified through a standard statistical analyses using three key diagnostic global metrics: RMS plate velocities, NLR characteristics, and TM behaviour. Additionally, models were assessed for consistency with published global paleomagnetic data, and for ages 〈 80 Ma for predicted relative hotspot motion, track geometry and time‐dependence. Optimised APM models demonstrated significantly improved global fit with geological and geophysical observations whilst performing consistently with geodynamic constraints. Critically, APM models derived by limiting average rates of NLR to ~0.05 °/Myr and absolute TM velocities to ~27 mm/yr fit geological observations including hotspot tracks. This suggests that this range of NLR and TM estimates may be appropriate for Earth over the last 220 Myr, providing a key step toward the practical integration of numerical geodynamics into plate tectonic reconstructions.
    Print ISSN: 2169-9313
    Electronic ISSN: 2169-9356
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    An open-source software environment for visualizing and refining plate tectonic reconstructions using high-resolution geological and geophysical data sets (2012)
    Geological Society of America (GSA)
    In: GSA Today
    Details
    Publication Date: 2012-03-30
    Description: We describe a powerful method to explore spatio-temporal relationships within geological and geophysical data sets by analyzing the data within the context of tectonic reconstructions. GPlates is part of a new generation of plate reconstruction software that incorporates functionality familiar from GIS software with the added dimension of geological time. Here we use GPlates to reconstruct geological terranes, geophysical grids, and paleomagnetic data within alternative tectonic models of the assembly of Western Australia and the configuration of Rodinia. With the ability to rapidly visualize a diverse range of geological and geophysical constraints within different reconstructions, users can easily investigate the implications of different tectonic models for reconciling a variety of observations and make more informed choices between different models and data.
    Print ISSN: 1052-5173
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 8
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    Full-fit, palinspastic reconstruction of the conjugate Australian-Antarctic margins (2011)
    Wiley
    In: Tectonics
    Details
    Publication Date: 2011-12-15
    Description: Despite decades of study the prerift configuration and early rifting history between Australia and Antarctica is not well established. The plate boundary system during the Cretaceous includes the evolving Kerguelen–Broken Ridge Large Igneous Province in the west as well as the conjugate passive and transform margin segments of the Australian and Antarctic continents. Previous rigid plate reconstruction models have highlighted the difficulty in satisfying all the available observations within a single coherent reconstruction history. We investigate a range of scenarios for the early rifting history of these plates by developing a deforming plate model for this conjugate margin pair. Potential field data are used to define the boundaries of stretched continental crust on a regional scale. Integrating crustal thickness along tectonic flow lines provides an estimate of the prerift location of the continental plate boundary. We then use the prerift plate boundary positions, along with additional constraints from geological structures and large igneous provinces within the same Australian and Antarctic plate system, to compute “full-fit” poles of rotation for Australia relative to Antarctica. Our preferred model implies that the Leeuwin and Vincennes Fracture Zones are conjugate features within Gondwana, but that the direction of initial opening between Australia and Antarctica does not follow the orientation of these features; rather, the geometry of these features is likely related to the earlier rifting of India away from Australia-Antarctica. Previous full-fit reconstructions, based on qualitative estimates of continental margin overlaps, generally yield a tighter fit than our preferred reconstruction based on palinspastic margin restoration.
    Print ISSN: 0278-7407
    Electronic ISSN: 1944-9194
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Revised Tectonic Evolution of the Eastern Indian Ocean (2013)
    Wiley
    Details
    Publication Date: 2013-03-20
    Description: [1]  Published plate tectonic models for the Australian-Antarctic plate pair imply geologically improbable scenarios at either, or both, ends of the Cretaceous rift and spreading system. Controversy also exists around the location of and motion at the plate boundary extending west of Australia-Antarctica, through the Kerguelen Plateau region. We present a plate tectonic model of relative motions among India, Australia and Antarctica from the onset of continental rifting to the establishment of rapid seafloor spreading, at ~43 Ma. The model conforms to a wide range of geological/geophysical evidence and reconstructs the formation of both the western Kerguelen region and the eastern Tasman region. The incorporation of spatio-temporally continuous plate boundaries reveals the presence of a plate boundary beneath the contiguous Central Kerguelen Plateau and Broken Ridge for ~65 million years. [2]  To investigate the relationship between the plate boundary system and the Kerguelen plume we test three alternative absolute reference frames. Using a fixed hotspot reference frame, the Indian Ocean mid-ocean ridge system remains within 500 km of the Kerguelen plume, while the proximity of the plate boundaries and the plume is more variable with a moving hotspot reference frame. Proximity between the plume, plate boundaries, and the Central Kerguelen Plateau/Broken Ridge for ~65Myrs, suggests that these specific features were not formed by a single, short-lived (5-10 Myr) pulse of magmatic activity, but rather bya ~25 Myr period of relatively high magma flux followed by ~40 Myr period of lower volume magmatic activity, an interpretation not excluded by the relatively sparse dredge and drill ages.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    A reconstruction of the Eurekan Orogeny incorporating deformation constraints (2017)
    Wiley
    In: Tectonics
    Details
    Publication Date: 2017-01-01
    Description: The Eurekan Orogeny records Paleogene convergence between Greenland and the Canadian Arctic. The complexity of the region, well represented by the disputed magnitude of Cenozoic sinistral displacement of Greenland relative to Ellesmere Island, stems from the simultaneous evolution of multiple tectonic regimes, as well as overprinting of later tectonic activity. Presented here is a plate model of regional crustal deformation constructed with the interactive GPlates software that enables an evaluation of previous reconstructions of the Eurekan Orogeny. This model is built upon a synthesis of published geological and geophysical data and their interpretations. It incorporates two phases of deformation from ~63-35 Ma. Phase one, ~63 to ~55 Ma, involves ~85 km of Paleocene extension between Ellesmere and Devon Island, extension of ~20 km between Axel Heiberg and Ellesmere Island, and ~85 km of sinistral strike-slip along the Nares Strait/Judge Daly Fault System, matching a range of 50-100 km indicated by the offset of marker beds, facies contacts, and platform margins between the conjugate Greenland and Ellesmere Island margins. Phase two, ~55 to 35 Ma, results in total east-west compression of ~30 km and ~200 km of north-south compression across Ellesmere Island. This model confirms, for the first time, that key observations from sub-regions deformed by the Eurekan Orogeny are compatible on a broad scale. We have also identified potential problem areas in southwestern Ellesmere Island that are less compatible with a best-fit model, given current constraints. This deforming plate model offers a platform and base model for future research.
    Print ISSN: 0278-7407
    Electronic ISSN: 1944-9194
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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