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Wouter P Schellart - One of the best experts on this subject based on the ideXlab platform.
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a geodynamic model of subduction evolution and slab detachment to explain Australian Plate acceleration and deceleration during the latest cretaceous early cenozoic
Lithosphere, 2017Co-Authors: Wouter P SchellartAbstract:During the latest Cretaceous-early Cenozoic, the northern margin of the Australian Plate was characterized by a large (4000 km wide) northto northeast-dipping subduction zone (New Guinea-Pocklington subduction zone) consuming a marginal basin. Geological and geophysical data imply that the subduction zone was active ca. 71-50 Ma, and suggest that it was responsible for Plate acceleration from ~1.0 to ~7.3 cm/yr ca. 64-59 Ma, and Plate deceleration from ~7.3 to ~0.3 cm/yr at 52-49 Ma. This paper presents a numerical model of buoyancy-driven subduction to test if the rates of Australian Plate acceleration and deceleration can be ascribed to the progressive evolution of a subducting slab. The geodynamic model reproduces the first-order Plate velocity evolution of the Australian Plate, with a transient ~5 m.y. period of acceleration from 2 to 8 cm/yr during upper mantle slab lengthening, an ~5 m.y. period of rapid Plate motion (~5-8 cm/yr), and a short, 3.9 m.y., period of Plate deceleration, starting with a 2 cm/yr velocity drop during 3.1 m.y. of continental subduction and followed by ~0.8 m.y. of rapid deceleration (4 cm/yr velocity drop) during slab detachment. The geodynamic model demonstrates that Plate velocity increases or decreases of ~4-6 cm/yr can occur over a period lasting < 1 m.y. to a few million years, comparable to what is observed for the latest Cretaceous-early Cenozoic evolution of the Australian Plate. Such rates of Plate acceleration and deceleration could be tested against Plate kinematic data for other subduction settings on Earth.
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Australian Plate motion and topography linked to fossil new guinea slab below lake eyre
Earth and Planetary Science Letters, 2015Co-Authors: Wouter P Schellart, Wim SpakmanAbstract:Abstract Unravelling causes for absolute Plate velocity change and continental dynamic topography change is challenging because of the interdependence of large-scale geodynamic driving processes. Here, we unravel a clear spatio-temporal relation between latest Cretaceous–Early Cenozoic subduction at the northern edge of the Australian Plate, Early Cenozoic Australian Plate motion changes and Cenozoic topography evolution of the Australian continent. We present evidence for a ∼4000 km wide subduction zone, which culminated in ophiolite obduction and arc-continent collision in the New Guinea–Pocklington Trough region during subduction termination, coinciding with cessation of spreading in the Coral Sea, a ∼5 cm/yr decrease in northward Australian Plate velocity, and slab detachment. Renewed northward motion caused the Australian Plate to override the sinking subduction remnant, which we detect with seismic tomography at 800–1200 km depth in the mantle under central-southeast Australia at a position predicted by our absolute Plate reconstructions. With a numerical model of slab sinking and mantle flow we predict a long-wavelength subsidence (negative dynamic topography) migrating southward from ∼50 Ma to present, explaining Eocene–Oligocene subsidence of the Queensland Plateau, ∼330 m of late Eocene–early Oligocene subsidence in the Gulf of Carpentaria, Oligocene–Miocene subsidence of the Marion Plateau, and providing a first-order fit to the present-day, ∼200 m deep, topographic depression of the Lake Eyre Basin and Murray–Darling Basin. We propound that dynamic topography evolution provides an independent means to couple geological processes to a mantle reference frame. This is complementary to, and can be integrated with, other approaches such as hotspot and slab reference frames.
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tracking the Australian Plate motion through the cenozoic constraints from 40ar 39ar geochronology
Tectonics, 2013Co-Authors: B E Cohen, K M Knesel, Paulo M Vasconcelos, Wouter P SchellartAbstract:Here we use geochronology of Australian intraPlate volcanoes to construct a high-resolution Plate-velocity record and to explore how tectonic events in the southwest Pacific may have influenced Plate motion. Nine samples from five volcanoes yield ages from 33.6 ± 0.5 to 27.3 ± 0.4 Ma and, when combined with published ages from 30 to 16 Ma, show that the rate of volcanic migration was not constant. Instead, the results indicate distinct changes in Australian Plate motion. Fast northward velocities (61 ± 8 and 57 ± 4 km/Ma) prevailed from 34 to 30 (±0.5) and from 23 to 16 (±0.5) Ma, respectively, with distinct reductions to 20 ± 10 and 22 ± 5 km/Ma from 30 to 29 (±0.5) Ma and from 26 to 23 (±0.5) Ma. These velocity reductions are concurrent with tectonic collisions in New Guinea and Ontong Java, respectively. Interspersed between the periods of sluggish motion is a brief 29-26 (±0.5) Ma burst of atypically fast northward Plate movement of 100 ± 20 km/Ma. We evaluate potential mechanisms for this atypically fast velocity, including catastrophic slab penetration into the lower mantle, thermomechanical erosion of the lithosphere, and plume-push forces; none are appropriate. This period of fast motion was, however, coincident with a major southward propagating slab tear that developed along the northeastern Plate margin, following partial jamming of subduction and ophiolite obduction in New Caledonia. Although it is unclear whether such an event can play a role in driving fast Plate motion, numerical or analogue models may help address this question. Key Points We determine nine 40Ar/39Ar ages from five Cenozoic volcanoes in Australia Slow velocities correlate with New Guinea and Ontong Java collisions Anomalously fast velocity of 100 +/- 20 km/Ma is identified from 29-26 Ma
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introduction to the thematic issue on the evolution and dynamics of the indo Australian Plate
Australian Journal of Earth Sciences, 2012Co-Authors: Myra Keep, Wouter P SchellartAbstract:The Australian Plate and the Indian Plate, initially formed from the breakup of Gondwana, became the Indo-Australian Plate in the Middle Eocene some 45–40 million years ago as both Plates amalgamat...
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evaluating slab Plate coupling in the indo Australian Plate
Geology, 2005Co-Authors: Mike Sandiford, David Coblentz, Wouter P SchellartAbstract:Distributed seismicity in the central Indian Ocean affords a unique opportunity to evaluate the extent of slab-Plate coupling in the Indo-Australian Plate. The mix of reverse-fault and strike-slip mechanisms in this region, with northwest-southeast to north-south maximum horizontal stress, S Hmax , implies that the effective slab pull is no more than ∼10% of the total negative buoyancy operating on the subducting slab. Numerical models of the intraPlate stress field predict a slab-pull component along the Sumatra and Java boundary segments of 2.82 ± 0.82 and 0.89 ± 0.35 × 10 12 N·m −1 , respectively. Mantle tomographic constraints coupled with insights from analogue modeling suggest that the differences relate to variations in the depth extent of the slabs and the degree of slab support provided by the transition zone. These results help resolve apparent contradictions between insights from intraPlate stress fields and Plate dynamics; i.e., although Plate motion is dominated by subduction, slab pull is only poorly expressed in the intraPlate stress field because of low slab-Plate coupling.
Wim Spakman - One of the best experts on this subject based on the ideXlab platform.
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Australian Plate motion and topography linked to fossil new guinea slab below lake eyre
Earth and Planetary Science Letters, 2015Co-Authors: Wouter P Schellart, Wim SpakmanAbstract:Abstract Unravelling causes for absolute Plate velocity change and continental dynamic topography change is challenging because of the interdependence of large-scale geodynamic driving processes. Here, we unravel a clear spatio-temporal relation between latest Cretaceous–Early Cenozoic subduction at the northern edge of the Australian Plate, Early Cenozoic Australian Plate motion changes and Cenozoic topography evolution of the Australian continent. We present evidence for a ∼4000 km wide subduction zone, which culminated in ophiolite obduction and arc-continent collision in the New Guinea–Pocklington Trough region during subduction termination, coinciding with cessation of spreading in the Coral Sea, a ∼5 cm/yr decrease in northward Australian Plate velocity, and slab detachment. Renewed northward motion caused the Australian Plate to override the sinking subduction remnant, which we detect with seismic tomography at 800–1200 km depth in the mantle under central-southeast Australia at a position predicted by our absolute Plate reconstructions. With a numerical model of slab sinking and mantle flow we predict a long-wavelength subsidence (negative dynamic topography) migrating southward from ∼50 Ma to present, explaining Eocene–Oligocene subsidence of the Queensland Plateau, ∼330 m of late Eocene–early Oligocene subsidence in the Gulf of Carpentaria, Oligocene–Miocene subsidence of the Marion Plateau, and providing a first-order fit to the present-day, ∼200 m deep, topographic depression of the Lake Eyre Basin and Murray–Darling Basin. We propound that dynamic topography evolution provides an independent means to couple geological processes to a mantle reference frame. This is complementary to, and can be integrated with, other approaches such as hotspot and slab reference frames.
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surface deformation and slab mantle interaction during banda arc subduction rollback
Nature Geoscience, 2010Co-Authors: Wim Spakman, Robert HallAbstract:The reason for the spectacular curvature of the Banda subduction zone is debated. Tomographic images and Plate reconstructions reveal subduction of a single slab. The ancient geometry of the Australian Plate, as well as the interaction between the slab and the mantle, caused the deformation of the slab. The spectacularly curved Banda arc comprises young oceanic crust1,2 enclosed by a volcanic inner arc, outer arc islands and a trough parallel to the Australian continental margin3,4,5. Strong seismic activity in the upper mantle defines a folded surface6,7, for which there are two contrasting explanations: deformation of a single slab5,8 or two separate slabs subducting from the north and south6,9. Here we combine seismic tomography with the Plate tectonic evolution of the region to infer that the Banda arc results from subduction of a single slab. Our palaeogeographic reconstruction shows that a Jurassic embayment, which consisted of dense oceanic lithosphere enclosed by continental crust, once existed within the Australian Plate. Banda subduction began about 15 million years ago when active Java subduction tore eastwards into the embayment. The present morphology of the subducting slab is only partially controlled by the shape of the embayment. As the Australian Plate moved northward at a high speed of about 7 cm yr−1, the Banda oceanic slab rolled back towards the south–southeast accompanied by active delamination separating the crust from the denser mantle. Increasing resistance of the mantle to Plate motion progressively folded the slab and caused strong deformation of the crust. The Banda arc represents an outstanding example of large-scale deformation of the Earth’s crust in response to coupling between the crust, slab and surrounding mantle.
K M Knesel - One of the best experts on this subject based on the ideXlab platform.
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40ar 39ar geochronology and volume estimates of the tasmantid seamounts support for a change in the motion of the Australian Plate
Journal of Volcanology and Geothermal Research, 2017Co-Authors: Tracey J Crossingham, Paulo M Vasconcelos, Toby Cunningham, K M KneselAbstract:Abstract New volume estimates and 40Ar/39Ar ages for the Tasmantid Seamounts are reported to investigate the origin of volcanism and potential links between volcanism and changes in the speed and direction of migration of the Australian Plate during the Cenozoic. The results show that the average extrusive volume of individual volcanoes along the seamount chain is 2587 ± 3078 km3 (1 s), and that volumes generally increase towards the south. An exception, the Britannia Guyot, located in the middle of the seamount chain, is the most voluminous (11,374 km3). Nineteen new 40Ar/39Ar ages, from Wreck to Gascoyne, show that the emplacement of the Tasmantid Seamounts occurred between 33.2 ± 1.5 and 6.5 ± 0.6 Ma. A single linear regression applied to the age versus latitude data, assuming volcanism to be caused by Plate migration over a stationary hotspot, reveals a Plate migration rate of 62 ± 2 kmMa− 1 (R2 = 0.97; n = 27) between ~ 33 and 6 Ma. However, the bend in the seamount track, corresponding with the period of largest eruptive volumes, suggests three distinct segments in the Tasmantid age versus latitude data. The northern segment is consistent with a Plate migration rate of 75 ± 10 kmMa− 1 (R2 = 0.88; n = 10) and the southern segment reveals a Plate migration rate of 64 ± 4 kmMa− 1 (R2 = 0.94; n = 17). The period between these two segments, from ~ 25 to 19 Ma, overlaps with the period of slow migration and change in the direction of the Australian Plate derived from the age versus latitude distribution of continental central volcanoes. The new Tasmantid Seamount results support the interpretation that there were changes in the velocity and direction to Australia's northward trajectory, possibly resulting from a series of collisional events.
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tracking the Australian Plate motion through the cenozoic constraints from 40ar 39ar geochronology
Tectonics, 2013Co-Authors: B E Cohen, K M Knesel, Paulo M Vasconcelos, Wouter P SchellartAbstract:Here we use geochronology of Australian intraPlate volcanoes to construct a high-resolution Plate-velocity record and to explore how tectonic events in the southwest Pacific may have influenced Plate motion. Nine samples from five volcanoes yield ages from 33.6 ± 0.5 to 27.3 ± 0.4 Ma and, when combined with published ages from 30 to 16 Ma, show that the rate of volcanic migration was not constant. Instead, the results indicate distinct changes in Australian Plate motion. Fast northward velocities (61 ± 8 and 57 ± 4 km/Ma) prevailed from 34 to 30 (±0.5) and from 23 to 16 (±0.5) Ma, respectively, with distinct reductions to 20 ± 10 and 22 ± 5 km/Ma from 30 to 29 (±0.5) Ma and from 26 to 23 (±0.5) Ma. These velocity reductions are concurrent with tectonic collisions in New Guinea and Ontong Java, respectively. Interspersed between the periods of sluggish motion is a brief 29-26 (±0.5) Ma burst of atypically fast northward Plate movement of 100 ± 20 km/Ma. We evaluate potential mechanisms for this atypically fast velocity, including catastrophic slab penetration into the lower mantle, thermomechanical erosion of the lithosphere, and plume-push forces; none are appropriate. This period of fast motion was, however, coincident with a major southward propagating slab tear that developed along the northeastern Plate margin, following partial jamming of subduction and ophiolite obduction in New Caledonia. Although it is unclear whether such an event can play a role in driving fast Plate motion, numerical or analogue models may help address this question. Key Points We determine nine 40Ar/39Ar ages from five Cenozoic volcanoes in Australia Slow velocities correlate with New Guinea and Ontong Java collisions Anomalously fast velocity of 100 +/- 20 km/Ma is identified from 29-26 Ma
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rapid changes in Australian Plate velocity due to collisions in new guinea and ontong java indicated by high resolution 40ar 39ar geochronology of Australian intraPlate volcanoes
AGU Fall Meeting Abstracts, 2011Co-Authors: B E Cohen, K M Knesel, Paulo M VasconcelosAbstract:Subduction zones are the most complex tectonic environments on Earth, as exemplified by the dynamic subduction systems in the southwest Pacific that have undergone numerous episodes of collisional orogenesis, slab rollback, initiation of new subduction zones, and subduction polarity reversal during the Cenozoic. One of the major challenges in modern geodynamics is to understand the timing and duration of these events within subduction zones, where the evidence may be variably obscured by difficult access in remote, rugged, vegetated, or submarine terrains, overprinting by subsequent tectonism, or even loss of evidence if rocks are subducted. A powerful approach to determine the age and duration of tectonic events within subduction zones is the record of paleo-Plate velocities for the interacting Plates; changes in Plate velocity are recorded by deviations in the geometry and age progression of plume-derived intraPlate volcanic chains. On the Australian Plate high-resolution 40Ar/39Ar geochronology of hotspot-derived volcanism has resolved a 3-Ma duration (from 26 to 23 Ma) reduction in Plate velocity, attributed to collision with the Ontong Java Plateau (Knesel et al. 2008, Nature vol. 454, p754-757). In this abstract, we report further geochronology of Australian intraPlate volcanoes, which demonstrates an earlier episode of reduced Plate velocity spanning from 30.5 to 29 Ma. This period of reduced velocity is correlated to collisional orogenesis in New Guinea or New Caledonia, which caused the cessation of convergence along the Papuan-Rennel trench and intensification of subduction along the Manus-Kilinailu-North Solomon system. The brief duration of this episode of reduced Plate velocity - spanning just over one million years - underscores the rapidity with which Plate boundaries can respond through the cessation of subduction along one system, and the resultant intensification of subduction along another zone.
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rapid change in drift of the Australian Plate records collision with ontong java Plateau
Nature, 2008Co-Authors: K M Knesel, B E Cohen, Paulo M Vasconcelos, D S ThiedeAbstract:Earth's largest and thickest oceanic Plateau, the Ontong Java Plateau, is currently colliding with the Australian Plate, but it has been difficult to date the start of this momentous event with much accuracy. Now a team from the University of Queensland presents strong evidence for a collision starting about 26 million years ago. The dating comes from geochronological data on hotspot volcanoes in the Tasman Sea, east of Australia, which reveal a link between collision of the Plateau with the Melanesian arc and motion of the Australian Plate. The timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks in the Pacific, including the archetypal Hawaiian chain, suggesting that immense oceanic Plateaus, like Ontong Java, can contribute to initiating rapid change in Plate boundaries and motions on a global scale. Geochronological data on hotspot volcanoes in eastern Australia are presented, which reveal a strong link between collision of the Plateau with the Melanesian arc and motion of the Australian Plate. The timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks in the Pacific, including the archetypal Hawaiian chain, and thus provide strong evidence that immense oceanic Plateaus can contribute to initiating rapid change in Plate boundaries and motions on a global scale. The subduction of oceanic Plateaux, which contain extraordinarily thick basaltic crust and are the marine counterparts of continental flood-basalt provinces, is an important factor in many current models of Plate motion1,2,3,4 and provides a potential mechanism for triggering Plate reorganization5. To evaluate such models, it is essential to decipher the history of the collision between the largest and thickest of the world’s oceanic Plateaux, the Ontong Java Plateau, and the Australian Plate, but this has been hindered by poor constraints for the arrival of the Plateau at the Melanesian trench. Here we present 40Ar–39Ar geochronological data on hotspot volcanoes in eastern Australian that reveal a strong link between collision of the Greenland-sized Ontong Java Plateau with the Melanesian arc and motion of the Australian Plate. The new ages define a short-lived period of reduced northward Plate motion between 26 and 23 Myr ago, coincident with an eastward offset in the contemporaneous tracks of seamount chains in the Tasman Sea east of Australia. These features record a brief westward deflection of the Australian Plate as the Plateau entered and choked the Melanesian trench 26 Myr ago. From 23 Myr ago, Australia returned to a rapid northerly trajectory at roughly the same time that southwest-directed subduction began along the Trobriand trough6. The timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks on the Pacific Plate, including the archetypal Hawaiian chain7, and thus provide strong evidence that immense oceanic Plateaux, like the Ontong Java, can contribute to initiating rapid change in Plate boundaries and motions on a global scale.
Douwe J J Van Hinsbergen - One of the best experts on this subject based on the ideXlab platform.
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retracted early cretaceous origin of the woyla arc sumatra indonesia on the Australian Plate
Earth and Planetary Science Letters, 2018Co-Authors: El Advokaat, Cg Langereis, Mayke L M Bongers, Alfend Rudyawan, M K Boudagherfadel, Douwe J J Van HinsbergenAbstract:Abstract Key to understanding the Plate kinematic evolution of the Neotethys oceanic domain that existed between the Gondwana-derived Indian and Australian continents in the south, and Eurasia in the north, is the reconstruction of oceanic Plates that are now entirely lost to subduction. Relics of these oceanic Plates exist in the form of ophiolites and island arcs accreted to the orogen that stretches from Tibet and the Himalayas to SE Asia that formed the southern margin of Sundaland. The intra-oceanic Woyla Arc thrusted over western Sundaland – the Eurasian core of SE Asia – in the mid-Cretaceous. The Woyla Arc was previously interpreted to have formed above a west-dipping subduction zone in the Early Cretaceous, synchronous with east-dipping subduction below Sundaland. The oceanic ‘Ngalau Plate’ between the Woyla Arc and Sundaland was lost to subduction. We present paleomagnetic results from Lower Cretaceous limestones and volcaniclastic rocks of the Woyla Arc, Middle Jurassic radiolarian cherts of the intervening Ngalau Plate, and Upper Jurassic–Lower Cretaceous detrital sediments of the Sundaland margin. Our results suggest that the Woyla Arc was formed around equatorial latitudes and only underwent an eastward longitudinal motion relative to Sundaland. This is consistent with a scenario where the Woyla Arc was formed on the edge of the Australian Plate. We propose a reconstruction where the Ngalau Plate formed a triangular oceanic basin between the N–S trending Woyla Arc and the NW-SE trending Sundaland margin to account for the absence of accreted arc rocks in the Himalayas. As consequence of this triangular geometry, accretion of the Woyla Arc to the western Sundaland margin was diachronous, accommodated by a southward migrating triple junction. Continuing convergence of the Australia relative to Eurasia was accommodated by subduction polarity reversal behind the Woyla Arc, possibly recorded by Cretaceous ophiolites in the Indo-Burman Ranges and the Andaman-Nicobar Islands.
Paulo M Vasconcelos - One of the best experts on this subject based on the ideXlab platform.
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40ar 39ar geochronology and volume estimates of the tasmantid seamounts support for a change in the motion of the Australian Plate
Journal of Volcanology and Geothermal Research, 2017Co-Authors: Tracey J Crossingham, Paulo M Vasconcelos, Toby Cunningham, K M KneselAbstract:Abstract New volume estimates and 40Ar/39Ar ages for the Tasmantid Seamounts are reported to investigate the origin of volcanism and potential links between volcanism and changes in the speed and direction of migration of the Australian Plate during the Cenozoic. The results show that the average extrusive volume of individual volcanoes along the seamount chain is 2587 ± 3078 km3 (1 s), and that volumes generally increase towards the south. An exception, the Britannia Guyot, located in the middle of the seamount chain, is the most voluminous (11,374 km3). Nineteen new 40Ar/39Ar ages, from Wreck to Gascoyne, show that the emplacement of the Tasmantid Seamounts occurred between 33.2 ± 1.5 and 6.5 ± 0.6 Ma. A single linear regression applied to the age versus latitude data, assuming volcanism to be caused by Plate migration over a stationary hotspot, reveals a Plate migration rate of 62 ± 2 kmMa− 1 (R2 = 0.97; n = 27) between ~ 33 and 6 Ma. However, the bend in the seamount track, corresponding with the period of largest eruptive volumes, suggests three distinct segments in the Tasmantid age versus latitude data. The northern segment is consistent with a Plate migration rate of 75 ± 10 kmMa− 1 (R2 = 0.88; n = 10) and the southern segment reveals a Plate migration rate of 64 ± 4 kmMa− 1 (R2 = 0.94; n = 17). The period between these two segments, from ~ 25 to 19 Ma, overlaps with the period of slow migration and change in the direction of the Australian Plate derived from the age versus latitude distribution of continental central volcanoes. The new Tasmantid Seamount results support the interpretation that there were changes in the velocity and direction to Australia's northward trajectory, possibly resulting from a series of collisional events.
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tracking the Australian Plate motion through the cenozoic constraints from 40ar 39ar geochronology
Tectonics, 2013Co-Authors: B E Cohen, K M Knesel, Paulo M Vasconcelos, Wouter P SchellartAbstract:Here we use geochronology of Australian intraPlate volcanoes to construct a high-resolution Plate-velocity record and to explore how tectonic events in the southwest Pacific may have influenced Plate motion. Nine samples from five volcanoes yield ages from 33.6 ± 0.5 to 27.3 ± 0.4 Ma and, when combined with published ages from 30 to 16 Ma, show that the rate of volcanic migration was not constant. Instead, the results indicate distinct changes in Australian Plate motion. Fast northward velocities (61 ± 8 and 57 ± 4 km/Ma) prevailed from 34 to 30 (±0.5) and from 23 to 16 (±0.5) Ma, respectively, with distinct reductions to 20 ± 10 and 22 ± 5 km/Ma from 30 to 29 (±0.5) Ma and from 26 to 23 (±0.5) Ma. These velocity reductions are concurrent with tectonic collisions in New Guinea and Ontong Java, respectively. Interspersed between the periods of sluggish motion is a brief 29-26 (±0.5) Ma burst of atypically fast northward Plate movement of 100 ± 20 km/Ma. We evaluate potential mechanisms for this atypically fast velocity, including catastrophic slab penetration into the lower mantle, thermomechanical erosion of the lithosphere, and plume-push forces; none are appropriate. This period of fast motion was, however, coincident with a major southward propagating slab tear that developed along the northeastern Plate margin, following partial jamming of subduction and ophiolite obduction in New Caledonia. Although it is unclear whether such an event can play a role in driving fast Plate motion, numerical or analogue models may help address this question. Key Points We determine nine 40Ar/39Ar ages from five Cenozoic volcanoes in Australia Slow velocities correlate with New Guinea and Ontong Java collisions Anomalously fast velocity of 100 +/- 20 km/Ma is identified from 29-26 Ma
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rapid changes in Australian Plate velocity due to collisions in new guinea and ontong java indicated by high resolution 40ar 39ar geochronology of Australian intraPlate volcanoes
AGU Fall Meeting Abstracts, 2011Co-Authors: B E Cohen, K M Knesel, Paulo M VasconcelosAbstract:Subduction zones are the most complex tectonic environments on Earth, as exemplified by the dynamic subduction systems in the southwest Pacific that have undergone numerous episodes of collisional orogenesis, slab rollback, initiation of new subduction zones, and subduction polarity reversal during the Cenozoic. One of the major challenges in modern geodynamics is to understand the timing and duration of these events within subduction zones, where the evidence may be variably obscured by difficult access in remote, rugged, vegetated, or submarine terrains, overprinting by subsequent tectonism, or even loss of evidence if rocks are subducted. A powerful approach to determine the age and duration of tectonic events within subduction zones is the record of paleo-Plate velocities for the interacting Plates; changes in Plate velocity are recorded by deviations in the geometry and age progression of plume-derived intraPlate volcanic chains. On the Australian Plate high-resolution 40Ar/39Ar geochronology of hotspot-derived volcanism has resolved a 3-Ma duration (from 26 to 23 Ma) reduction in Plate velocity, attributed to collision with the Ontong Java Plateau (Knesel et al. 2008, Nature vol. 454, p754-757). In this abstract, we report further geochronology of Australian intraPlate volcanoes, which demonstrates an earlier episode of reduced Plate velocity spanning from 30.5 to 29 Ma. This period of reduced velocity is correlated to collisional orogenesis in New Guinea or New Caledonia, which caused the cessation of convergence along the Papuan-Rennel trench and intensification of subduction along the Manus-Kilinailu-North Solomon system. The brief duration of this episode of reduced Plate velocity - spanning just over one million years - underscores the rapidity with which Plate boundaries can respond through the cessation of subduction along one system, and the resultant intensification of subduction along another zone.
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rapid change in drift of the Australian Plate records collision with ontong java Plateau
Nature, 2008Co-Authors: K M Knesel, B E Cohen, Paulo M Vasconcelos, D S ThiedeAbstract:Earth's largest and thickest oceanic Plateau, the Ontong Java Plateau, is currently colliding with the Australian Plate, but it has been difficult to date the start of this momentous event with much accuracy. Now a team from the University of Queensland presents strong evidence for a collision starting about 26 million years ago. The dating comes from geochronological data on hotspot volcanoes in the Tasman Sea, east of Australia, which reveal a link between collision of the Plateau with the Melanesian arc and motion of the Australian Plate. The timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks in the Pacific, including the archetypal Hawaiian chain, suggesting that immense oceanic Plateaus, like Ontong Java, can contribute to initiating rapid change in Plate boundaries and motions on a global scale. Geochronological data on hotspot volcanoes in eastern Australia are presented, which reveal a strong link between collision of the Plateau with the Melanesian arc and motion of the Australian Plate. The timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks in the Pacific, including the archetypal Hawaiian chain, and thus provide strong evidence that immense oceanic Plateaus can contribute to initiating rapid change in Plate boundaries and motions on a global scale. The subduction of oceanic Plateaux, which contain extraordinarily thick basaltic crust and are the marine counterparts of continental flood-basalt provinces, is an important factor in many current models of Plate motion1,2,3,4 and provides a potential mechanism for triggering Plate reorganization5. To evaluate such models, it is essential to decipher the history of the collision between the largest and thickest of the world’s oceanic Plateaux, the Ontong Java Plateau, and the Australian Plate, but this has been hindered by poor constraints for the arrival of the Plateau at the Melanesian trench. Here we present 40Ar–39Ar geochronological data on hotspot volcanoes in eastern Australian that reveal a strong link between collision of the Greenland-sized Ontong Java Plateau with the Melanesian arc and motion of the Australian Plate. The new ages define a short-lived period of reduced northward Plate motion between 26 and 23 Myr ago, coincident with an eastward offset in the contemporaneous tracks of seamount chains in the Tasman Sea east of Australia. These features record a brief westward deflection of the Australian Plate as the Plateau entered and choked the Melanesian trench 26 Myr ago. From 23 Myr ago, Australia returned to a rapid northerly trajectory at roughly the same time that southwest-directed subduction began along the Trobriand trough6. The timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks on the Pacific Plate, including the archetypal Hawaiian chain7, and thus provide strong evidence that immense oceanic Plateaux, like the Ontong Java, can contribute to initiating rapid change in Plate boundaries and motions on a global scale.
