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Graeme Eagles - One of the best experts on this subject based on the ideXlab platform.
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Tectonic Reconstructions for paleobathymetry in Drake Passage
Tectonophysics, 2014Co-Authors: Graeme Eagles, Wilfried JokatAbstract:Abstract A minimum-complexity Tectonic Reconstruction, based on published and new basin opening models, depicts how the Scotia Sea grew by Cenozoic plate divergence, dismembering a Jurassic sheared margin of Gondwana. Part of the Jurassic–early Cretaceous ocean that accreted to this margin forms the core of the Central Scotia Plate, the arc plate above a trench at the eastern end of the Scotia Sea, which migrated east away from the Antarctic and South American plates. A sequence of extensional basins opened on the western edge of the Central Scotia Plate at 50–30 Ma, decoupled from the South American Plate to the northwest by slow motion on a long transform fault. Succeeding the basins, seafloor spreading started around 30 Ma on the West Scotia Ridge, which propagated northwards in the 23–17 Ma period and ceased to operate at 6 Ma. The circuits of plate motions inside and outside the Scotia Arc are joined via rotations that describe Antarctic–Central Scotia plate motion in Powell Basin until 20 Ma, and along the South Scotia Ridge thereafter. The modelled relative motion at the northern edge of the Scotia Sea is thus constrained only by the plate circuit, but nonetheless resembles that known coarsely from the geological record of Tierra del Fuego. A paleobathymetric interpretation of nine time slices in the model shows Drake Passage developing as an intermediate-depth oceanographic gateway at 50–30 Ma, with deep flow possible afterwards. Initially, this deep flow would have been made tortuous by numerous intermediate and shallow barriers. A frontal pattern resembling that in the modern Scotia Sea would have awaited the clearance of significant barriers by continuing seafloor spreading in the Scotia Sea at ~ 18.5 Ma, at Shag Rocks Passage, and after 10 Ma southeast of South Georgia.
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animated Tectonic Reconstruction of the southern pacific and alkaline volcanism at its convergent margins since eocene times
Tectonophysics, 2009Co-Authors: Graeme Eagles, Karsten Gohl, Robert D LarterAbstract:Abstract An animated Reconstruction shows South Pacific plate kinematics, in the reference frame of West Antarctica, between 55 Ma and the present-day. The ocean floor in the region formed due to seafloor spreading between the Antarctic, Pacific, Phoenix and Nazca plates (a plate formed by fragmentation of the Farallon plate early in Oligocene times). The Pacific–Antarctic Ridge remained fairly stable throughout this time, migrating relatively northwestwards, by various mechanisms, behind the rapidly-moving Pacific plate. The Nazca and Phoenix plates also moved quickly, but relatively towards the east or southeast, and were subducted in these directions beneath the South American and Antarctic plates. Segments of spreading centres forming at the trailing edges of the Nazca and Phoenix plates periodically collided with these subduction zones, resulting in the total destruction of the Nazca–Phoenix spreading centre and the partial destruction of the Nazca–Antarctica spreading centre (the Chile Ridge) and Antarctic–Phoenix Ridge, which ceased to operate shortly before its northeasternmost three segments could collide with the Antarctic margin. Following collision of segments of the Chile Ridge, parts of the Antarctic plate underwent subduction at the Chile Trench. After these collisions, slab windows should have formed beneath both the South American and Antarctic convergent margins, and the animation shows occurrences of alkaline volcanism that have been, or can newly be, related to them. Further occurrences of alkali basalts, at the margins of the Powell Basin and, more speculatively, James Ross Island, can be related to the formation of a slab window beneath them following the collision of segments of the South America–Antarctica spreading centre in the northwest Weddell Sea.
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Quantitative Tectonic Reconstructions of Zealandia based on crustal thickness estimates
Geochemistry Geophysics Geosystems, 2008Co-Authors: Jan Grobys, Karsten Gohl, Graeme EaglesAbstract:Zealandia is a key piece in the plate Reconstruction of Gondwana. The positions of its submarine plateaus are major constraints on the best fit and breakup involving New Zealand, Australia, Antarctica, and associated microplates. As the submarine plateaus surrounding New Zealand consist of extended and highly extended continental crust, classic plate Tectonic Reconstructions assuming rigid plates and narrow plate boundaries fail to reconstruct these areas correctly. However, if the early breakup history shall be reconstructed, it is crucial to consider crustal stretching in a plate-Tectonic Reconstruction. We present a Reconstruction of the basins around New Zealand (Great South Basin, Bounty Trough, and New Caledonia Basin) based on crustal balancing, an approach that takes into account the rifting and thinning processes affecting continental crust. In a first step, we computed a crustal thickness map of Zealandia using seismic, seismological, and gravity data. The crustal thickness map shows the submarine plateaus to have a uniform crustal thickness of 20–24 km and the basins to have a thickness of 12–16 km. We assumed that a Reconstruction of Zealandia should close the basins and lead to a most uniform crustal thickness. We used the standard deviation of the reconstructed crustal thickness as a measure of uniformity. The Reconstruction of the Campbell Plateau area shows that the amount of extension in the Bounty Trough and the Great South Basin is far smaller than previously thought. Our results indicate that the extension of the Bounty Trough and Great South Basin occurred simultaneously.
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South Pacific - the Tectonic Reconstruction movie
2005Co-Authors: Graeme Eagles, Karsten Gohl, Robert D LarterAbstract:Accurate Tectonic Reconstructions provide an essential framework for evaluating and modelling long-term palaeoenvironmental data. Reconstructions of large parts of the Pacific Ocean for mid-Cenozoic and earlier times are particularly difficult to constrain because it is almost encircled by subduction zones. However, in the southernmost Pacific the conjugate passive margins offshore from New Zealand and Marie Byrd Land provide an opportunity to produce well-constrained Reconstructions from the Late Cretaceous onwards. In addition to providing a framework for studying palaeoenvironmental evolution of the Southern Ocean, Reconstructions of this region are also the key link in the global plate circuit tying plate motions in the Pacific Ocean basin to the rest of the world (Cande et al., 1995). Until recently, however, the scarcity of marine geophysical data from the remote area off Marie Byrd Land has placed a severe limitation on the reliability of such Reconstructions. We present a new animated Reconstruction showing South Pacific plate kinematics since 90 Ma (Eagles et al., 2004). In this Reconstruction sections of the modern marine free-air gravity field are rotated with the Tectonic plates. Reconstruction of gridded data limits the problem of subjective interpretation of features used in Reconstructionsto identification of plate boundaries. Animation of Reconstructions is a useful way of illustrating kinematic evolution, and of exposing inconsistencies in Tectonic scenarios depicted by static Reconstructions. The combination of these two techniques provides a powerful new tool for considering the spatial and temporal context of palaeoenvironmentaldata. Future work will include integration of this Reconstruction with Reconstructions of the Tasman and Drake Passage gateways that flank the studied region, and production of gridded palaeobathymetric Reconstructions for use in palaeoclimate modelling.
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Plate-Tectonic Reconstruction of the southern Pacific and West Antarctica
2005Co-Authors: Karsten Gohl, Graeme EaglesAbstract:Accurate plate-kinematic Reconstructions at relatively high spatial and temporal resolution are the basis for understanding the opening of ocean basins and the evolution of seafloor relief and the effect it has had on controlling deep ocean current directions. We developed an animated, grid-based plate-kinematic Reconstruction of the southern Pacific Ocean from 90 Ma to present, using the satellite-derived gravity anomaly field, and interpolated isochrons and plate rotation parameters from both published and new studies using marine geophysical data. The earliest opening with formation of seafloor between Chatham Rise (New Zealand) and Thurston Island (West Antarctica) occurred at 92-90 Ma along a Pacific-Antarctic plate boundary developing along the Bounty Trough and Great South Basin of New Zealand. The break-up between Campbell Plateau and Marie Byrd Land began at 83 Ma. The onset of an independent motion of the Bellingshausen Plate adjacent to the West Antarctic margin can be estimated at 79 Ma. Its motion generated a transpressional eastern plate boundary. The Pacific-Bellingshausen spreading centre developed a set of long offset transform faults (e.g. Udintsev, Tharp, Heezen) that the Pacific-Antarctic plate boundary inherited around 61 Ma when the Bellingshausen plate ceased to move independently as part of a Pacific-wide plate Tectonic reorganization event. Southwest of these transforms, the Pacific-Antarctic Ridge saw an increase in transform-fault segmentation by about 58 Ma. At about 47 Ma, the Pacific-Phoenix Ridge jumped northward to directly link the Pacific-Antarctic ridge to the Pacific-Farallon ridge as a result of an unstable Pacific-Antarctic-Phoenix triple-junction configuration. Further Reconstruction time steps illustrate the development of the dominant transform and fracture zones systems in the South Pacific.
Robert D Larter - One of the best experts on this subject based on the ideXlab platform.
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animated Tectonic Reconstruction of the southern pacific and alkaline volcanism at its convergent margins since eocene times
Tectonophysics, 2009Co-Authors: Graeme Eagles, Karsten Gohl, Robert D LarterAbstract:Abstract An animated Reconstruction shows South Pacific plate kinematics, in the reference frame of West Antarctica, between 55 Ma and the present-day. The ocean floor in the region formed due to seafloor spreading between the Antarctic, Pacific, Phoenix and Nazca plates (a plate formed by fragmentation of the Farallon plate early in Oligocene times). The Pacific–Antarctic Ridge remained fairly stable throughout this time, migrating relatively northwestwards, by various mechanisms, behind the rapidly-moving Pacific plate. The Nazca and Phoenix plates also moved quickly, but relatively towards the east or southeast, and were subducted in these directions beneath the South American and Antarctic plates. Segments of spreading centres forming at the trailing edges of the Nazca and Phoenix plates periodically collided with these subduction zones, resulting in the total destruction of the Nazca–Phoenix spreading centre and the partial destruction of the Nazca–Antarctica spreading centre (the Chile Ridge) and Antarctic–Phoenix Ridge, which ceased to operate shortly before its northeasternmost three segments could collide with the Antarctic margin. Following collision of segments of the Chile Ridge, parts of the Antarctic plate underwent subduction at the Chile Trench. After these collisions, slab windows should have formed beneath both the South American and Antarctic convergent margins, and the animation shows occurrences of alkaline volcanism that have been, or can newly be, related to them. Further occurrences of alkali basalts, at the margins of the Powell Basin and, more speculatively, James Ross Island, can be related to the formation of a slab window beneath them following the collision of segments of the South America–Antarctica spreading centre in the northwest Weddell Sea.
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South Pacific - the Tectonic Reconstruction movie
2005Co-Authors: Graeme Eagles, Karsten Gohl, Robert D LarterAbstract:Accurate Tectonic Reconstructions provide an essential framework for evaluating and modelling long-term palaeoenvironmental data. Reconstructions of large parts of the Pacific Ocean for mid-Cenozoic and earlier times are particularly difficult to constrain because it is almost encircled by subduction zones. However, in the southernmost Pacific the conjugate passive margins offshore from New Zealand and Marie Byrd Land provide an opportunity to produce well-constrained Reconstructions from the Late Cretaceous onwards. In addition to providing a framework for studying palaeoenvironmental evolution of the Southern Ocean, Reconstructions of this region are also the key link in the global plate circuit tying plate motions in the Pacific Ocean basin to the rest of the world (Cande et al., 1995). Until recently, however, the scarcity of marine geophysical data from the remote area off Marie Byrd Land has placed a severe limitation on the reliability of such Reconstructions. We present a new animated Reconstruction showing South Pacific plate kinematics since 90 Ma (Eagles et al., 2004). In this Reconstruction sections of the modern marine free-air gravity field are rotated with the Tectonic plates. Reconstruction of gridded data limits the problem of subjective interpretation of features used in Reconstructionsto identification of plate boundaries. Animation of Reconstructions is a useful way of illustrating kinematic evolution, and of exposing inconsistencies in Tectonic scenarios depicted by static Reconstructions. The combination of these two techniques provides a powerful new tool for considering the spatial and temporal context of palaeoenvironmentaldata. Future work will include integration of this Reconstruction with Reconstructions of the Tasman and Drake Passage gateways that flank the studied region, and production of gridded palaeobathymetric Reconstructions for use in palaeoclimate modelling.
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High‐resolution animated Tectonic Reconstruction of the South Pacific and West Antarctic Margin
Geochemistry Geophysics Geosystems, 2004Co-Authors: Graeme Eagles, Karsten Gohl, Robert D LarterAbstract:[1] An animated Reconstruction shows South Pacific plate kinematics between 90 and 45 Ma, using the satellite-derived gravity anomaly field, interpolated isochrons and plate rotation parameters from both published and new work on marine geophysical data. The Great South Basin and Bounty Trough, New Zealand, are shown as the earliest Pacific–Antarctic plate boundary that opened before 83 Ma. The earliest true Pacific–Antarctic seafloor formed within the eastern parts of this boundary, but later and farther west, seafloor formed within its Antarctic flank. After 80 Ma, the Bellingshausen plate converged with an oceanic part of the Antarctic plate to its east, while its motion simultaneously caused rifting in continental Antarctica to the south. The Pacific–Bellingshausen spreading center developed a set of long offset transform faults that the Pacific–Antarctic plate boundary inherited around chron C27 when the Bellingshausen plate ceased to move independently as part of a Pacific-wide plate Tectonic reorganization event. Southwest of these transforms the Pacific–Antarctic Ridge saw an increase in transform-fault segmentation by ∼58 Ma. One of the long offset Pacific–Bellingshausen transforms, referred to as “V,” was modified during the C27 reorganization event when a Pacific–Antarctic–Phoenix triple junction initiated on its southern edge. Eastern parts of “V” started to operate in the Pacific–Phoenix spreading system, lengthening it even more, while its western parts operated in the Pacific–Antarctic system. This complicated feature was by-passed and deactivated by ridge axis propagation to its northwest at ∼47 Ma. We interpret our animation to highlight possible connections between these events.
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high resolution animated Tectonic Reconstruction of the south pacific and west antarctic margin
Geochemistry Geophysics Geosystems, 2004Co-Authors: Graeme Eagles, Karsten Gohl, Robert D LarterAbstract:[1] An animated Reconstruction shows South Pacific plate kinematics between 90 and 45 Ma, using the satellite-derived gravity anomaly field, interpolated isochrons and plate rotation parameters from both published and new work on marine geophysical data. The Great South Basin and Bounty Trough, New Zealand, are shown as the earliest Pacific–Antarctic plate boundary that opened before 83 Ma. The earliest true Pacific–Antarctic seafloor formed within the eastern parts of this boundary, but later and farther west, seafloor formed within its Antarctic flank. After 80 Ma, the Bellingshausen plate converged with an oceanic part of the Antarctic plate to its east, while its motion simultaneously caused rifting in continental Antarctica to the south. The Pacific–Bellingshausen spreading center developed a set of long offset transform faults that the Pacific–Antarctic plate boundary inherited around chron C27 when the Bellingshausen plate ceased to move independently as part of a Pacific-wide plate Tectonic reorganization event. Southwest of these transforms the Pacific–Antarctic Ridge saw an increase in transform-fault segmentation by ∼58 Ma. One of the long offset Pacific–Bellingshausen transforms, referred to as “V,” was modified during the C27 reorganization event when a Pacific–Antarctic–Phoenix triple junction initiated on its southern edge. Eastern parts of “V” started to operate in the Pacific–Phoenix spreading system, lengthening it even more, while its western parts operated in the Pacific–Antarctic system. This complicated feature was by-passed and deactivated by ridge axis propagation to its northwest at ∼47 Ma. We interpret our animation to highlight possible connections between these events.
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Detailed Tectonic Reconstruction of the Southern Pacific
2004Co-Authors: Karsten Gohl, Graeme Eagles, Robert D LarterAbstract:Accurate plate-kinematic Reconstructions at relatively high spatial and temporal resolution are the basis for understanding the opening of ocean basins and the evolution of seafloor relief and the effect it has had on controlling deep ocean current directions. We developed an animated, grid-based plate-kinematic Reconstruction of the southern Pacific Ocean from 90 Ma to present, using the satellite-derived gravity anomaly field, and interpolated isochrons and plate rotation parameters from both published and new studies using marine geophysical data. The earliest opening with formation of seafloor between Chatham Rise (New Zealand) and Thurston Island (West Antarctica) occurred at 92-90 Ma along a Pacific-Antarctic plate boundary developing along the Bounty Trough and Great South Basin of New Zealand. The break-up between Campbell Plateau and Marie Byrd Land began at 83 Ma. The onset of an independent motion of the Bellingshausen Plate adjacent to the West Antarctic margin can be estimated at 79 Ma. Its motion generated a transpressional eastern plate boundary. The Pacific-Bellingshausen spreading centre developed a set of long offset transform faults (e.g. Udintsev, Tharp, Heezen) that the Pacific-Antarctic plate boundary inherited around 61 Ma when the Bellingshausen plate ceased to move independently as part of a Pacific-wide plate Tectonic reorganization event. Southwest of these transforms, the Pacific-Antarctic Ridge saw an increase in transform-fault segmentation by about 58 Ma. At about 47 Ma, the Pacific-Phoenix Ridge jumped northward to directly link the Pacific-Antarctic ridge to the Pacific-Farallon ridge as a result of an unstable Pacific-Antarctic-Phoenix triple-junction configuration. Further Reconstruction time steps illustrate the development of the dominant transform and fracture zones systems in the South Pacific.
Karsten Gohl - One of the best experts on this subject based on the ideXlab platform.
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Playing jigsaw with Large Igneous Provinces—A plate Tectonic Reconstruction of Ontong Java Nui, West Pacific
Geochemistry Geophysics Geosystems, 2015Co-Authors: Katharina Hochmuth, Karsten Gohl, Gabriele Uenzelmann-nebenAbstract:The three largest Large Igneous Provinces (LIP) of the western Pacific—Ontong Java, Manihiki, and Hikurangi Plateaus—were emplaced during the Cretaceous Normal Superchron and show strong similarities in their geochemistry and petrology. The plate Tectonic relationship between those LIPs, herein referred to as Ontong Java Nui, is uncertain, but a joined emplacement was proposed by Taylor (2006). Since this hypothesis is still highly debated and struggles to explain features such as the strong differences in crustal thickness between the different plateaus, we revisited the joined emplacement of Ontong Java Nui in light of new data from the Manihiki Plateau. By evaluating seismic refraction/wide-angle reflection data along with seismic reflection records of the margins of the proposed “Super”-LIP, a detailed scenario for the emplacement and the initial phase of breakup has been developed. The LIP is a result of an interaction of the arriving plume head with the Phoenix-Pacific spreading ridge in the Early Cretaceous. The breakup of the LIP shows a complicated interplay between multiple microplates and Tectonic forces such as rifting, shearing, and rotation. Our plate kinematic model of the western Pacific incorporates new evidence from the breakup margins of the LIPs, the Tectonic fabric of the seafloor, as well as previously published Tectonic concepts such as the rotation of the LIPs. The updated rotation poles of the western Pacific allow a detailed plate Tectonic Reconstruction of the region during the Cretaceous Normal Superchron and highlight the important role of LIPs in the plate Tectonic framework.
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playing jigsaw with large igneous provinces a plate Tectonic Reconstruction of ontong java nui west pacific
Geochemistry Geophysics Geosystems, 2015Co-Authors: Katharina Hochmuth, Karsten Gohl, Gabriele UenzelmannnebenAbstract:The three largest Large Igneous Provinces (LIP) of the western Pacific—Ontong Java, Manihiki, and Hikurangi Plateaus—were emplaced during the Cretaceous Normal Superchron and show strong similarities in their geochemistry and petrology. The plate Tectonic relationship between those LIPs, herein referred to as Ontong Java Nui, is uncertain, but a joined emplacement was proposed by Taylor (2006). Since this hypothesis is still highly debated and struggles to explain features such as the strong differences in crustal thickness between the different plateaus, we revisited the joined emplacement of Ontong Java Nui in light of new data from the Manihiki Plateau. By evaluating seismic refraction/wide-angle reflection data along with seismic reflection records of the margins of the proposed “Super”-LIP, a detailed scenario for the emplacement and the initial phase of breakup has been developed. The LIP is a result of an interaction of the arriving plume head with the Phoenix-Pacific spreading ridge in the Early Cretaceous. The breakup of the LIP shows a complicated interplay between multiple microplates and Tectonic forces such as rifting, shearing, and rotation. Our plate kinematic model of the western Pacific incorporates new evidence from the breakup margins of the LIPs, the Tectonic fabric of the seafloor, as well as previously published Tectonic concepts such as the rotation of the LIPs. The updated rotation poles of the western Pacific allow a detailed plate Tectonic Reconstruction of the region during the Cretaceous Normal Superchron and highlight the important role of LIPs in the plate Tectonic framework.
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Playing jigsaw with large igneous provinces - a plate-Tectonic Reconstruction of Omtong Java Nui
The EGU General Assembly, 2015Co-Authors: Katharina Hochmuth, Karsten Gohl, Gabriele Uenzelmann-neben, Reinhard WernerAbstract:Ontong Java Nui is a Cretaceous large igneous province (LIP), which was rifted apart into various smaller plateaus shortly after its emplacement around 125 Ma in the central Pacific. It incorporated the Ontong Java Plateau, the Hikurangi Plateau and the Manihiki Plateau as well as multiple smaller fragments, which have been subducted. Its size has been estimated to be approximately 0.8% of the Earth’s surface. A volcanic edifice of this size has potentially had a great impact on the environment such as its CO2 release. The break-up of the “Super”-LIP is poorly constrained, because the break-up and subsequent seafloor spreading occurred within the Cretaceous Quiet Period. The Manihiki Plateau is presumably the centerpiece of this “Super”-LIP and shows by its margins and internal fragmentation that its Tectonic and volcanic activity is related to the break-up of Ontong Java Nui. By incorporating two new seismic refraction/wide-angle reflection lines across two of the main sub-plateaus of the Manihiki Plateau, we can classify the break-up modes of the individual margins of the Manihiki Plateau. The Western Plateaus experienced crustal stretching due to the westward motion of the Ontong Java Plateau. The High Plateau shows sharp strike-slip movements at its eastern boundary towards an earlier part of Ontong Java Nui, which is has been subducted, and a rifted margin with a strong volcanic overprint at its southern edges towards the Hikurangi Plateau. These observations allow us a re-examination of the conjugate margins of the Hikurangi Plateau and the Ontong Java Plateau. The repositioning of the different plateaus leads to the conclusion that Ontong Java Nui was larger (~1.2% of the Earth’s surface at emplacement) than previously anticipated. We use these finding to improve the plate Tectonic Reconstruction of the Cretaceous Pacific and to illuminate the role of the LIPs within the plate Tectonic circuit in the western and central Pacific.
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animated Tectonic Reconstruction of the southern pacific and alkaline volcanism at its convergent margins since eocene times
Tectonophysics, 2009Co-Authors: Graeme Eagles, Karsten Gohl, Robert D LarterAbstract:Abstract An animated Reconstruction shows South Pacific plate kinematics, in the reference frame of West Antarctica, between 55 Ma and the present-day. The ocean floor in the region formed due to seafloor spreading between the Antarctic, Pacific, Phoenix and Nazca plates (a plate formed by fragmentation of the Farallon plate early in Oligocene times). The Pacific–Antarctic Ridge remained fairly stable throughout this time, migrating relatively northwestwards, by various mechanisms, behind the rapidly-moving Pacific plate. The Nazca and Phoenix plates also moved quickly, but relatively towards the east or southeast, and were subducted in these directions beneath the South American and Antarctic plates. Segments of spreading centres forming at the trailing edges of the Nazca and Phoenix plates periodically collided with these subduction zones, resulting in the total destruction of the Nazca–Phoenix spreading centre and the partial destruction of the Nazca–Antarctica spreading centre (the Chile Ridge) and Antarctic–Phoenix Ridge, which ceased to operate shortly before its northeasternmost three segments could collide with the Antarctic margin. Following collision of segments of the Chile Ridge, parts of the Antarctic plate underwent subduction at the Chile Trench. After these collisions, slab windows should have formed beneath both the South American and Antarctic convergent margins, and the animation shows occurrences of alkaline volcanism that have been, or can newly be, related to them. Further occurrences of alkali basalts, at the margins of the Powell Basin and, more speculatively, James Ross Island, can be related to the formation of a slab window beneath them following the collision of segments of the South America–Antarctica spreading centre in the northwest Weddell Sea.
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Quantitative Tectonic Reconstructions of Zealandia based on crustal thickness estimates
Geochemistry Geophysics Geosystems, 2008Co-Authors: Jan Grobys, Karsten Gohl, Graeme EaglesAbstract:Zealandia is a key piece in the plate Reconstruction of Gondwana. The positions of its submarine plateaus are major constraints on the best fit and breakup involving New Zealand, Australia, Antarctica, and associated microplates. As the submarine plateaus surrounding New Zealand consist of extended and highly extended continental crust, classic plate Tectonic Reconstructions assuming rigid plates and narrow plate boundaries fail to reconstruct these areas correctly. However, if the early breakup history shall be reconstructed, it is crucial to consider crustal stretching in a plate-Tectonic Reconstruction. We present a Reconstruction of the basins around New Zealand (Great South Basin, Bounty Trough, and New Caledonia Basin) based on crustal balancing, an approach that takes into account the rifting and thinning processes affecting continental crust. In a first step, we computed a crustal thickness map of Zealandia using seismic, seismological, and gravity data. The crustal thickness map shows the submarine plateaus to have a uniform crustal thickness of 20–24 km and the basins to have a thickness of 12–16 km. We assumed that a Reconstruction of Zealandia should close the basins and lead to a most uniform crustal thickness. We used the standard deviation of the reconstructed crustal thickness as a measure of uniformity. The Reconstruction of the Campbell Plateau area shows that the amount of extension in the Bounty Trough and the Great South Basin is far smaller than previously thought. Our results indicate that the extension of the Bounty Trough and Great South Basin occurred simultaneously.
Suzanne Y. O'reilly - One of the best experts on this subject based on the ideXlab platform.
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Early Paleozoic Tectonic Reconstruction of Iran: Tales from detrital zircon geochronology
Lithos, 2017Co-Authors: Hadi Shafaii Moghadam, William L. Griffin, Robert J. Stern, Tonny B. Thomsen, Guido Meinhold, Reza Aharipour, Suzanne Y. O'reillyAbstract:In this study we use detrital zircons to probe the Early Paleozoic history of NE Iran and evaluate the link between sediment sources and Gondwanan pre-Cadomian, Cadomian and younger events. U–Pb zircon ages and Hf isotopic compositions are reported for detrital zircons from Ordovician and Early Devonian sedimentary rocks from NE Iran. These clastic rocks are dominated by zircons with major age populations at ~ 2.5 Ga, ~ 0.8–0.6 Ga, 0.5 Ga and ~ 0.5–0.4 Ga as well as a minor broad peak at ~ 1.0 Ga. The source of 2.5 Ga detrital zircons is enigmatic; they may have been supplied from the Saharan Metacraton (or West African Craton) to the southwest or Afghanistan–Tarim to the east. The detrital zircons with age populations at 0.8–0.6 Ga probably originated from Cryogenian–Ediacaran juvenile igneous rocks of the Arabian–Nubian Shield; this inference is supported by their juvenile Hf isotopes, although some negative εHf (t) values suggest that other sources (such as the West African Craton) were also involved. The age peak at ca 0.5 Ga correlates with Cadomian magmatism reported from Iranian basement and elsewhere in north Gondwana. The variable εHf (t) values of Cadomian detrital zircons, resembling the εHf (t) values of zircons in magmatic Cadomian rocks from Iran and Taurides (Turkey), suggest an Andean-type margin and the involvement of reworked older crust in the generation of the magmatic rocks. The youngest age population at 0.5–0.4 Ga is interpreted to represent Gondwana rifting and the opening of Paleotethys, which probably started in Late Cambrian–Ordovician time. A combination of U–Pb dating and Hf-isotope data from Iran, Turkey and North Gondwana confirms that Iran and Turkey were parts of Gondwana at least until late Paleozoic time
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Early Paleozoic Tectonic Reconstruction of Iran: tales from detrital zircon geochronology
Lithos, 2016Co-Authors: Hadi Shafaii Moghadam, William L. Griffin, Robert J. Stern, Tonny B. Thomsen, Guido Meinhold, Reza Aharipour, Suzanne Y. O'reillyAbstract:Abstract In this study we use detrital zircons to probe the Early Paleozoic history of NE Iran and evaluate the link between sediment sources and Gondwanan pre-Cadomian, Cadomian and younger events. U–Pb zircon ages and Hf isotopic compositions are reported for detrital zircons from Ordovician and Early Devonian sedimentary rocks from NE Iran. These clastic rocks are dominated by zircons with major age populations at ~ 2.5 Ga, ~ 0.8–0.6 Ga, 0.5 Ga and ~ 0.5–0.4 Ga as well as a minor broad peak at ~ 1.0 Ga. The source of 2.5 Ga detrital zircons is enigmatic; they may have been supplied from the Saharan Metacraton (or West African Craton) to the southwest or Afghanistan–Tarim to the east. The detrital zircons with age populations at 0.8–0.6 Ga probably originated from Cryogenian–Ediacaran juvenile igneous rocks of the Arabian–Nubian Shield; this inference is supported by their juvenile Hf isotopes, although some negative eHf (t) values suggest that other sources (such as the West African Craton) were also involved. The age peak at ca 0.5 Ga correlates with Cadomian magmatism reported from Iranian basement and elsewhere in north Gondwana. The variable eHf (t) values of Cadomian detrital zircons, resembling the eHf (t) values of zircons in magmatic Cadomian rocks from Iran and Taurides (Turkey), suggest an Andean-type margin and the involvement of reworked older crust in the generation of the magmatic rocks. The youngest age population at 0.5–0.4 Ga is interpreted to represent Gondwana rifting and the opening of Paleotethys, which probably started in Late Cambrian–Ordovician time. A combination of U–Pb dating and Hf-isotope data from Iran, Turkey and North Gondwana confirms that Iran and Turkey were parts of Gondwana at least until late Paleozoic time.
Rudy Swennen - One of the best experts on this subject based on the ideXlab platform.
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Pleistocene-Holocene Tectonic Reconstruction of the Ballık travertine (Denizli Graben, SW Turkey): (De)formation of large travertine geobodies at intersecting grabens
Journal of Structural Geology, 2019Co-Authors: Koen Van Noten, Savaş Topal, M. Oruç Baykara, Mehmet Özkul, Hannes Claes, Cihan Aratman, Rudy SwennenAbstract:Abstract Travertine geobodies have been identified as potential reservoir analogues to carbonate build-ups in pre-salt hydrocarbon systems. To investigate travertine geobody deformation, faults were mapped in 35 travertine quarries that excavate the Ballik travertine, i.e. a c. 12.5 km2 large travertine geobody that precipitated at the intersection of the NE margin of the Denizli Basin and neighbouring Baklan Graben (SW Turkey). This travertine precipitated from cooling carbonate-saturated thermal spring waters that resurfaced along the margin fracture/fault network and through Neogene unconsolidated underlying sediments. From the Denizli basin floor to the uplifted graben shoulders, fault orientation is dominantly WNW-ESE oriented with major basin faults showing a left-stepping trend. Along the upper Denizli margin, travertine is only deformed by extensional normal faults. Along the lower margin, travertine starts with a subhorizontal facies but evolves to a travertine facies formed by a sloping topography with a domal architecture. Paleostress inversion of fault-slip data reveals that an Early Pleistocene NNE-SSW extensional-transtensional phase initiated the WNW-ESE oriented, graben-facing normal fault network. In the Middle Pleistocene, the Ballik fault network was left-lateral strike-slip reactivated because it acted as a transfer zone between the NW-SE extending neighbouring Baklan Basin and NW-SE extension along NE-SW oriented margin faults of the DGHS. In this stress configuration, travertine precipitated along the SW margin fault of the Baklan Graben. After strike-slip reactivation, a Late Pleistocene-to-current NNE-SSW extensional stress regime reinstalled during which margin faults widened and active travertine precipitation moved to more central parts of the DGHS. As different Tectonic regimes affect graben intersections, reservoir analogues can have a complex deformation history driven by fault reactivation and recurrent stress permutations. This study concludes that large travertine geobodies can form at graben intersections because of their susceptibility to enhanced fluid flow through the complex fault-fracture network.
