scholarly journals A Late Cretaceous true polar wander oscillation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ross N. Mitchell ◽  
Christopher J. Thissen ◽  
David A. D. Evans ◽  
Sarah P. Slotznick ◽  
Rodolfo Coccioni ◽  
...  
Keyword(s):  
High Resolution ◽  
Late Cretaceous ◽  
Plate Tectonics ◽  
Large Scale ◽  
Spin Axis ◽  
Polar Wander ◽  
The Past ◽  
True Polar Wander ◽  
Palaeomagnetic Data

AbstractTrue polar wander (TPW), or planetary reorientation, is well documented for other planets and moons and for Earth at present day with satellites, but testing its prevalence in Earth’s past is complicated by simultaneous motions due to plate tectonics. Debate has surrounded the existence of Late Cretaceous TPW ca. 84 million years ago (Ma). Classic palaeomagnetic data from the Scaglia Rossa limestone of Italy are the primary argument against the existence of ca. 84 Ma TPW. Here we present a new high-resolution palaeomagnetic record from two overlapping stratigraphic sections in Italy that provides evidence for a ~12° TPW oscillation from 86 to 78 Ma. This observation represents the most recent large-scale TPW documented and challenges the notion that the spin axis has been largely stable over the past 100 million years.

Late Cretaceous True Polar Wander: Not So Fast

Science ◽  
2000 ◽  
Vol 288 (5475) ◽  
pp. 2283a-2283 ◽  
Author(s):  
R. D. Cottrell
Keyword(s):  
Late Cretaceous ◽  
Polar Wander ◽  
True Polar Wander

Inverted South China: A novel configuration for Rodinia and its breakup

Geology ◽  
2020 ◽  
Author(s):  
Xianqing Jing ◽  
David A.D. Evans ◽  
Zhenyu Yang ◽  
Yabo Tong ◽  
Yingchao Xu ◽  
...  
Keyword(s):  
South China ◽  
Plate Tectonics ◽  
The South ◽  
Polar Wander ◽  
True Polar Wander ◽  
Apparent Polar Wander Path ◽  
Lower Member ◽  
New Interpretation ◽  
Global Data

Disentangling records of Rodinia fragmentation and true polar wander remains a challenge for understanding late Tonian plate tectonics. The ca. 760 Ma lower member of the Liántuó Formation, South China, yields a primary paleomagnetic remanence that passes both the fold and reversal tests. This new result and recently reported ca. 800 Ma data from elsewhere in South China suggest a new interpretation of its apparent polar wander path, whereby pre–770 Ma poles have inverted absolute polarity relative to traditional interpretations. Based on this inversion, and an interpretation of several oscillations of true polar wander documented by global data during 810–760 Ma, we propose a novel reconstruction for Rodinia and its breakup. Our reconstruction places the South China, India, and Kalahari cratons to the southwest of Laurentia, with connections that might have been established as early as ca. 1000 Ma. Our model also suggests that initial rifting of Rodinia occurred at ca. 800 Ma via fast northward motion of the India craton and South China.

A high resolution reanalysis for the Mediterranean Sea

2021 ◽  
Author(s):  
Romain Escudier ◽  
Emanuela Clementi ◽  
Mohamed Omar ◽  
Andrea Cipollone ◽  
Jenny Pistoia ◽  
...  
Keyword(s):  
High Resolution ◽  
Mediterranean Sea ◽  
Large Scale ◽  
Thermohaline Circulation ◽  
Deep Convection ◽  
Horizontal Resolution ◽  
Continuous Increase ◽  
The Past ◽  
The Mediterranean

<p>In order to be able to predict the future ocean climate and weather, it is crucial to understand what happened in the past and the mechanisms responsible for the ocean variability. This is particularly true in a complex area such as the Mediterranean Sea with diverse dynamics such as deep convection and thermohaline circulation or coastal hydrodynamics. To this end, effective tools are reanalyses or reconstructions of the past ocean state. </p><p>Here we present a new physical reanalysis of the Mediterranean Sea at high resolution, developed in the Copernicus Marine Environment Monitoring Service (CMEMS) framework. The hydrodynamic model is based on the Nucleus for European Modelling of the Ocean (NEMO) combined with a variational data assimilation scheme (OceanVar).</p><p>The model has a horizontal resolution of 1/24<strong>°</strong> and 141 vertical z* levels and provides daily and monthly 3D values of temperature, salinity, sea level and currents. Hourly ECMWF ERA-5 atmospheric fields force the model and daily boundary conditions in the Atlantic are taken from the global CMCC C-GLORS reanalysis. 39 rivers model the freshwater input to the basin plus the Dardanelles. The reanalysis covers 33-years, initialized from SeaDataNet climatology in January 1985, getting to a nominal state after a two-years spin-up and ending in 2019. In-situ data from CTD, ARGO floats and XBT are assimilated into the model in combination with satellite altimetry data.</p><p>This reanalysis has been validated and assessed through comparison to in-situ and satellite observations as well as literature climatologies. The results show an overall improvement of the skill and a better representation of the main dynamics of the region compared to the previous, lower resolution (1/16<strong>°</strong>) reanalysis. Temperature and salinity RMSE is decreased by respectively 12% and 20%. The deeper biases in salinity of the previous version are corrected and the new reanalysis present a better representation of the deep convection in the Gulf of Lion. Climate signals show continuous increase of the temperature due to climate change but also in salinity.</p><p>The new reanalysis will allow the study of physical processes at multi-scales, from the large scale to the transient small mesoscale structures.</p>

Paleopoles and paleolatitudes of North America and speculations about displaced terrains

1979 ◽  
Vol 16 (3) ◽  
pp. 669-694 ◽  
Author(s):  
E. Irving
Keyword(s):  
North America ◽  
Plate Tectonics ◽  
Early Carboniferous ◽  
Coast Range ◽  
Present Position ◽  
Polar Wander ◽  
The Past ◽  
Western Cordillera ◽  
Middle Paleozoic ◽  
Single Path

A statistically determined path of apparent polar wander for the past 300 Ma for North America is given. It has a zigzag form, the bends corresponding to important changes in the drift of North America. Many Mesozoic and Early Tertiary paleopoles from the Western Cordillera do not conform to this path, and they are best explained by motions of miniblocks within the Cordillera. Especially notable is the displacement of Vancouver Island and associated Alaskan terrains (Wrangellia) in the early Mesozoic, and the clockwise rotation of the Coast Range of Oregon and Washington (Siletzia) in the Cenozoic. Limited evidence indicates that part at least of the Northern Appalachian region could have been about 10° south of its present position relative to North America in Late Devonian and Early Carboniferous times, and that it achieved its present position by Late Carboniferous time. Displaced terrains of early and middle Paleozoic age may also be present in the Appalachians. Displacements in the Appalachians and Cordillera could have been caused by the exchange of fragments of continental crust across transcurrent plate junctures. Apparent polar wandering paths for the Precambrian are tentative, but a fairly simple single path can be constructed for all structural provinces of the Laurentian Shield. This reconstruction of a single Precambrian path is supported by agreement among approximately contemporaneous paleopoles from widespread localities. It implies that movements amongst the structural provinces of the shield during the Hudsonian and Grenvillian Orogenies have been modest, and perhaps not in excess of about 1000 km in a latitude sense. This idea has been disputed by those who would apply conventional ideas of plate-tectonics to the Proterozoic, but it has the merit of explaining all the paleopoles and their geological relationships in a comparatively simple unified scheme. Rates of latitude change in the Precambrian may have been over twice as great as in the Phanerozoic.

scholarly journals A High Resolution Reanalysis for the Mediterranean Sea

2021 ◽  
Vol 9 ◽  
Author(s):  
Romain Escudier ◽  
Emanuela Clementi ◽  
Andrea Cipollone ◽  
Jenny Pistoia ◽  
Massimiliano Drudi ◽  
...  
Keyword(s):  
High Resolution ◽  
Mediterranean Sea ◽  
Sea Level ◽  
Large Scale ◽  
Mixed Layer Depth ◽  
Horizontal Resolution ◽  
Continuous Increase ◽  
The Past ◽  
The Mediterranean

In order to be able to forecast the weather and estimate future climate changes in the ocean, it is crucial to understand the past and the mechanisms responsible for the ocean variability. This is particularly true in a complex area such as the Mediterranean Sea with diverse dynamics like deep convection and overturning circulation. To this end, effective tools are ocean reanalyses or reconstructions of the past ocean state. Here we present a new physical reanalysis of the Mediterranean Sea at high resolution, developed in the Copernicus Marine Environment Monitoring Service (CMEMS) framework. The hydrodynamic model is based on the Nucleus for European Modelling of the Ocean (NEMO) combined with a variational data assimilation scheme (OceanVar). The model has a horizontal resolution of 1/24° and 141 unevenly distributed vertical z* levels. It provides daily and monthly temperature, salinity, current, sea level and mixed layer depth as well as hourly fields for surface velocities and sea level. ECMWF ERA-5 atmospheric fields force the model and daily boundary conditions in the Atlantic are taken from a global reanalysis. The reanalysis covers the 33 years from 1987 to 2019. Initialized from SeaDataNet climatology in January 1985, it reaches a nominal state after a 2-years spin-up. In-situ data from CTD, ARGO floats and XBT are assimilated into the model in combination with satellite altimetry observations. This reanalysis has been validated and assessed through comparison to in-situ and satellite observations as well as literature climatologies. The results show an overall improvement of the comparison with observations and a better representation of the main dynamics of the region compared to a previous, lower resolution (1/16°), reanalysis. Temperature and salinity RMSD are decreased by respectively 14 and 18%. The salinity biases at depth of the previous version are corrected. Climate signals show continuous increase of the temperature and salinity, confirming estimates from observations and other reanalysis. The new reanalysis will allow the study of physical processes at multi-scales, from the large scale to the transient small mesoscale structures and the selection of climate indicators for the basin.

scholarly journals Earth evolution and dynamics—a tribute to Kevin Burke

2016 ◽  
Vol 53 (11) ◽  
pp. 1073-1087 ◽  
Author(s):  
Trond H. Torsvik ◽  
Bernhard Steinberger ◽  
Lewis D. Ashwal ◽  
Pavel V. Doubrovine ◽  
Reidar G. Trønnes
Keyword(s):  
Plate Tectonics ◽  
Large Scale ◽  
Plate Boundaries ◽  
Mantle Plumes ◽  
The Past ◽  
The Pacific ◽  
Igneous Provinces ◽  
After Effect ◽  
Essential Contribution ◽  
Lowermost Mantle

Kevin Burke’s original and thought-provoking contributions have been published steadily for the past 60 years, and more than a decade ago he set out to resolve how plate tectonics and mantle plumes interact by proposing a simple conceptual model, which we will refer to as the Burkian Earth. On the Burkian Earth, mantle plumes take us from the deepest mantle to sub-lithospheric depths, where partial melting occurs, and to the surface, where hotspot lavas erupt today, and where large igneous provinces and kimberlites have erupted episodically in the past. The arrival of a plume head contributes to continental break-up and punctuates plate tectonics by creating and modifying plate boundaries. Conversely, plate tectonics makes an essential contribution to the mantle through subduction. Slabs restore mass to the lowermost mantle and are the triggering mechanism for plumes that rise from the margins of the two large-scale low shear-wave velocity structures in the lowermost mantle, which Burke christened TUZO and JASON. Situated just above the core–mantle boundary, beneath Africa and the Pacific, these are stable and antipodal thermochemical piles, which Burke reasons represent the immediate after-effect of the moon-forming event and the final magma ocean crystallization.

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