Geological Society, London, Special Publications, 2016
The supercontinent-cycle hypothesis attributes planetary-scale episodic tectonic events to an int... more The supercontinent-cycle hypothesis attributes planetary-scale episodic tectonic events to an intrinsic self-organizing mode of mantle convection, governed by the buoyancy of continental lithosphere that resists subduction during closure of old ocean basins, and consequent reorganization of mantle convection cells leading to opening of new ocean basins. Characteristic timescales of the cycle are typically 500–700 myr. Proposed spatial patterns of cyclicity range from hemispheric (introversion) to antipodal (extroversion), to precisely between those end-members (orthoversion). Advances in our understanding can arise from theoretical or numerical modelling, primary data acquisition relevant to continental reconstructions, and spatiotemporal correlations between plate kinematics, geodynamic events and palaeoenvironmental history. The palaeogeographic record of supercontinental tectonics on Earth is still under development. The contributions in this special publication provide snap-shot...
State-of-the-art measurements of the direction and intensity of Earth's ancient magnetic fiel... more State-of-the-art measurements of the direction and intensity of Earth's ancient magnetic field have made important contributions to our understanding of the geology and palaeogeography of Precambrian Earth. The PALEOMAGIA and PINT(QPI) databases provide thorough public collections of important palaeomagnetic data of this kind. They comprise more than 4,100 observations in total and have been essential in supporting our international collaborative efforts to understand Earth's magnetic history on a timescale far longer than that of the present Phanerozoic Eon. Here, we provide an overview of the technical structure and applications of both databases, paying particular attention to recent improvements and discoveries.
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, Jan 28, 2017
The bulk Earth composition contains probably less than 0.3% of water, but this trace amount of wa... more The bulk Earth composition contains probably less than 0.3% of water, but this trace amount of water can affect the long-term evolution of the Earth in a number of different ways. The foremost issue is the occurrence of plate tectonics, which governs almost all aspects of the Earth system, and the presence of water could either promote or hinder the operation of plate tectonics, depending on where water resides. The global water cycle, which circulates surface water into the deep mantle and back to the surface again, could thus have played a critical role in the Earth's history. In this contribution, we first review the present-day water cycle and discuss its uncertainty as well as its secular variation. If the continental freeboard has been roughly constant since the Early Proterozoic, model results suggest long-term net water influx from the surface to the mantle, which is estimated to be 3-4.5×10(14) g yr(-1) on the billion years time scale. We survey geological and geochemic...
Geological Society, London, Special Publications, 2015
Moderate to high palaeolatitudes recorded in mafic dykes, exposed along the coast of Bahia, Brazi... more Moderate to high palaeolatitudes recorded in mafic dykes, exposed along the coast of Bahia, Brazil, are partly responsible for some interpretations that the São Francisco/Congo craton was separate from the low-latitude Rodinia supercontinent at about 1050 Ma. We report new palaeomagnetic data that replicate the previous results. However, we obtain substantially younger U–Pb baddeleyite ages from five dykes previously thought to be 1.02–1.01 Ga according to the 40Ar/39Ar method. Specifically, the so-called ‘A-normal’ remanence direction from Salvador is dated at 924.2±3.8 Ma, within error of the age for the ‘C’ remanence direction at 921.5±4.3 Ma. An ‘A-normal’ dyke at Ilhéus is dated at 926.1±4.6 Ma, and two ‘A-normal’ dykes at Olivença have indistinguishable ages with best estimate of emplacement at 918.2±6.7 Ma. We attribute the palaeomagnetic variance of the ‘A-normal’ and ‘C’ directions to lack of averaging of geomagnetic palaeosecular variation in some regions. Our results rend...
Within the North Dakota Little Missouri Badlands, a continuous succession of Cretaceous through l... more Within the North Dakota Little Missouri Badlands, a continuous succession of Cretaceous through lowermost Eocene age sediments exposes a nearly complete terrestrial Paleocene record. Using the K-T boundary as the basal datum, a ca.180 meter composite section of the lowermost Fort Union Formation has been constructed. Paleomagnetic samples that have been analyzed from this section demonstrate a series of geomagnetic
Analysis of Vendian to Cambrian paleomagnetic data shows anomalously fast rotations and latitudin... more Analysis of Vendian to Cambrian paleomagnetic data shows anomalously fast rotations and latitudinal drift for all of the major continents. These motions are consistent with an Early to Middle Cambrian inertial interchange true polar wander event, during which Earth's lithosphere and mantle rotated about 90 degrees in response to an unstable distribution of the planet's moment of inertia. The proposed event produces a longitudinally constrained Cambrian paleogeography and accounts for rapid rates of continental motion during that time.
Apparent Polar Wander paths based on high quality paleomagnetic poles are critical tools for eval... more Apparent Polar Wander paths based on high quality paleomagnetic poles are critical tools for evaluating paleogeographic reconstructions of Precambrian supercontinents. Recently such data have presented challenges to various reconstructions for the Neoproterozoic supercontinent, Rodinia. In light of these challenges it has become increasingly important to refine our understanding of the positions of two of the largest landmasses making up Rodinia,
A continuous succession of Cretaceous through lowermost Eocene terrestrial sediments contains a n... more A continuous succession of Cretaceous through lowermost Eocene terrestrial sediments contains a nearly complete Paleocene record, in the Little Missouri River Valley of North Dakota, USA. We aim to calibrate the rates of post-Cretaceous ecological recovery from mass ...
Current paleogeographic reconstructions for the Paleoproterozoic supercontinent Nuna depend large... more Current paleogeographic reconstructions for the Paleoproterozoic supercontinent Nuna depend largely on the paleolatitude and apparent polar wander path for Laurentia. This study updates and adds to the existing Paleoproterozoic APWP for Laurentia through a detailed paleomagnetic study of Dubawnt Supergroup (ca. 1.84-1.72 Ga), Nunavut, Canada. We have replicated the dual-polarity magnetization of the previously named "Dubawnt" pole produced by Park
The Namaqua-Natal Province of southern Africa formed a part of the Kalahari craton, possibly link... more The Namaqua-Natal Province of southern Africa formed a part of the Kalahari craton, possibly linked to the 1.0 Ga supercontinent Rodinia, but the timing of assembly and its positioning relation to other components is still debated. Thorough ion-probe zircon dating combined with ...
Geological Society, London, Special Publications, 2016
The supercontinent-cycle hypothesis attributes planetary-scale episodic tectonic events to an int... more The supercontinent-cycle hypothesis attributes planetary-scale episodic tectonic events to an intrinsic self-organizing mode of mantle convection, governed by the buoyancy of continental lithosphere that resists subduction during closure of old ocean basins, and consequent reorganization of mantle convection cells leading to opening of new ocean basins. Characteristic timescales of the cycle are typically 500–700 myr. Proposed spatial patterns of cyclicity range from hemispheric (introversion) to antipodal (extroversion), to precisely between those end-members (orthoversion). Advances in our understanding can arise from theoretical or numerical modelling, primary data acquisition relevant to continental reconstructions, and spatiotemporal correlations between plate kinematics, geodynamic events and palaeoenvironmental history. The palaeogeographic record of supercontinental tectonics on Earth is still under development. The contributions in this special publication provide snap-shot...
State-of-the-art measurements of the direction and intensity of Earth's ancient magnetic fiel... more State-of-the-art measurements of the direction and intensity of Earth's ancient magnetic field have made important contributions to our understanding of the geology and palaeogeography of Precambrian Earth. The PALEOMAGIA and PINT(QPI) databases provide thorough public collections of important palaeomagnetic data of this kind. They comprise more than 4,100 observations in total and have been essential in supporting our international collaborative efforts to understand Earth's magnetic history on a timescale far longer than that of the present Phanerozoic Eon. Here, we provide an overview of the technical structure and applications of both databases, paying particular attention to recent improvements and discoveries.
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, Jan 28, 2017
The bulk Earth composition contains probably less than 0.3% of water, but this trace amount of wa... more The bulk Earth composition contains probably less than 0.3% of water, but this trace amount of water can affect the long-term evolution of the Earth in a number of different ways. The foremost issue is the occurrence of plate tectonics, which governs almost all aspects of the Earth system, and the presence of water could either promote or hinder the operation of plate tectonics, depending on where water resides. The global water cycle, which circulates surface water into the deep mantle and back to the surface again, could thus have played a critical role in the Earth's history. In this contribution, we first review the present-day water cycle and discuss its uncertainty as well as its secular variation. If the continental freeboard has been roughly constant since the Early Proterozoic, model results suggest long-term net water influx from the surface to the mantle, which is estimated to be 3-4.5×10(14) g yr(-1) on the billion years time scale. We survey geological and geochemic...
Geological Society, London, Special Publications, 2015
Moderate to high palaeolatitudes recorded in mafic dykes, exposed along the coast of Bahia, Brazi... more Moderate to high palaeolatitudes recorded in mafic dykes, exposed along the coast of Bahia, Brazil, are partly responsible for some interpretations that the São Francisco/Congo craton was separate from the low-latitude Rodinia supercontinent at about 1050 Ma. We report new palaeomagnetic data that replicate the previous results. However, we obtain substantially younger U–Pb baddeleyite ages from five dykes previously thought to be 1.02–1.01 Ga according to the 40Ar/39Ar method. Specifically, the so-called ‘A-normal’ remanence direction from Salvador is dated at 924.2±3.8 Ma, within error of the age for the ‘C’ remanence direction at 921.5±4.3 Ma. An ‘A-normal’ dyke at Ilhéus is dated at 926.1±4.6 Ma, and two ‘A-normal’ dykes at Olivença have indistinguishable ages with best estimate of emplacement at 918.2±6.7 Ma. We attribute the palaeomagnetic variance of the ‘A-normal’ and ‘C’ directions to lack of averaging of geomagnetic palaeosecular variation in some regions. Our results rend...
Within the North Dakota Little Missouri Badlands, a continuous succession of Cretaceous through l... more Within the North Dakota Little Missouri Badlands, a continuous succession of Cretaceous through lowermost Eocene age sediments exposes a nearly complete terrestrial Paleocene record. Using the K-T boundary as the basal datum, a ca.180 meter composite section of the lowermost Fort Union Formation has been constructed. Paleomagnetic samples that have been analyzed from this section demonstrate a series of geomagnetic
Analysis of Vendian to Cambrian paleomagnetic data shows anomalously fast rotations and latitudin... more Analysis of Vendian to Cambrian paleomagnetic data shows anomalously fast rotations and latitudinal drift for all of the major continents. These motions are consistent with an Early to Middle Cambrian inertial interchange true polar wander event, during which Earth's lithosphere and mantle rotated about 90 degrees in response to an unstable distribution of the planet's moment of inertia. The proposed event produces a longitudinally constrained Cambrian paleogeography and accounts for rapid rates of continental motion during that time.
Apparent Polar Wander paths based on high quality paleomagnetic poles are critical tools for eval... more Apparent Polar Wander paths based on high quality paleomagnetic poles are critical tools for evaluating paleogeographic reconstructions of Precambrian supercontinents. Recently such data have presented challenges to various reconstructions for the Neoproterozoic supercontinent, Rodinia. In light of these challenges it has become increasingly important to refine our understanding of the positions of two of the largest landmasses making up Rodinia,
A continuous succession of Cretaceous through lowermost Eocene terrestrial sediments contains a n... more A continuous succession of Cretaceous through lowermost Eocene terrestrial sediments contains a nearly complete Paleocene record, in the Little Missouri River Valley of North Dakota, USA. We aim to calibrate the rates of post-Cretaceous ecological recovery from mass ...
Current paleogeographic reconstructions for the Paleoproterozoic supercontinent Nuna depend large... more Current paleogeographic reconstructions for the Paleoproterozoic supercontinent Nuna depend largely on the paleolatitude and apparent polar wander path for Laurentia. This study updates and adds to the existing Paleoproterozoic APWP for Laurentia through a detailed paleomagnetic study of Dubawnt Supergroup (ca. 1.84-1.72 Ga), Nunavut, Canada. We have replicated the dual-polarity magnetization of the previously named "Dubawnt" pole produced by Park
The Namaqua-Natal Province of southern Africa formed a part of the Kalahari craton, possibly link... more The Namaqua-Natal Province of southern Africa formed a part of the Kalahari craton, possibly linked to the 1.0 Ga supercontinent Rodinia, but the timing of assembly and its positioning relation to other components is still debated. Thorough ion-probe zircon dating combined with ...
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