scholarly journals On the scales of dynamic topography in whole-mantle convection models - preprint version

2017 ◽  
Author(s):  
Maëlis ARNOULD ◽  
Nicolas Coltice ◽  
Nicolas Flament ◽  
Valentin Seigneur ◽  
Dietmar Müller
Keyword(s):  
Mantle Convection ◽  
Dynamic Topography

scholarly journals The impact of rheological uncertainty on dynamic topography predictions

Solid Earth ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 2167-2178 ◽  
Author(s):  
Ömer F. Bodur ◽  
Patrice F. Rey
Keyword(s):  
Mantle Convection ◽  
Numerical Experiments ◽  
Mantle Flow ◽  
Dynamic Topography ◽  
Density Anomaly ◽  
Low Viscosity ◽  
Local Reduction ◽  
Dynamic Components ◽  
Mantle Rheology ◽  
The Impact

Abstract. Much effort is being made to extract the dynamic components of the Earth's topography driven by density heterogeneities in the mantle. Seismically mapped density anomalies have been used as an input into mantle convection models to predict the present-day mantle flow and stresses applied on the Earth's surface, resulting in dynamic topography. However, mantle convection models give dynamic topography amplitudes generally larger by a factor of ∼2, depending on the flow wavelength, compared to dynamic topography amplitudes obtained by removing the isostatically compensated topography from the Earth's topography. In this paper, we use 3-D numerical experiments to evaluate the extent to which the dynamic topography depends on mantle rheology. We calculate the amplitude of instantaneous dynamic topography induced by the motion of a small spherical density anomaly (∼100 km radius) embedded into the mantle. Our experiments show that, at relatively short wavelengths (<1000 km), the amplitude of dynamic topography, in the case of non-Newtonian mantle rheology, is reduced by a factor of ∼2 compared to isoviscous rheology. This is explained by the formation of a low-viscosity channel beneath the lithosphere and a decrease in thickness of the mechanical lithosphere due to induced local reduction in viscosity. The latter is often neglected in global mantle convection models. Although our results are strictly valid for flow wavelengths less than 1000 km, we note that in non-Newtonian rheology all wavelengths are coupled, and the dynamic topography at long wavelengths will be influenced.

scholarly journals Improving global paleogeography since the late Paleozoic using paleobiology

2017 ◽  
Author(s):  
Wenchao Cao ◽  
Sabin Zahirovic ◽  
Nicolas Flament ◽  
Simon Williams ◽  
Jan Golonka ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Mantle Convection ◽  
Growth Models ◽  
Plate Motion ◽  
Late Paleozoic ◽  
Plate Tectonic ◽  
Dynamic Topography ◽  
Tectonic Reconstructions ◽  
Marine Boundaries ◽  
Continental Growth

Abstract. Paleogeographic reconstructions are important to understand Earth's tectonic evolution, past eustatic and regional sea level change, hydrocarbon genesis, and to constrain and interpret the dynamic topography predicted by time-dependent global mantle convection models. Several global paleogeographic maps have been compiled and published but they are generally presented as static maps with varying temporal resolution and fixed spatial resolution. Existing global paleogeographic maps are also tied to a particular plate motion model, making it difficult to link them to alternative digital plate tectonic reconstructions. To address this limitation, we developed a workflow to reverse-engineer global paleogeographic maps to their present-day coordinates and enable them to be linked to any tectonic reconstruction. Published paleogeographic compilations are also tied to fixed input datasets. We used fossil data from the Paleobiology Database to identify inconsistencies between fossils paleo-environments and published paleogeographic maps, and to improve the location of inferred terrestrial-marine boundaries by resolving these inconsistencies. As a result, the overall consistency ratio between the paleogeography and fossil collections was improved from 76.9 % to 96.1 %. We estimated the surface areas of global paleogeographic features (shallow marine environments, landmasses, mountains and ice sheets), and reconstructed the global continental flooding history since the late Paleozoic based on the amended paleogeographies. Finally, we discuss the relationships between emerged land area and total continental crust area through time, continental growth models, and strontium isotope (87Sr/86Sr) signatures in ocean water. Our study highlights the flexibility of digital paleogeographic models linked to state-of-the-art plate tectonic reconstructions in order to better understand the interplay of continental growth and eustasy, with wider implications for understanding Earth's paleotopography, ocean circulation, and the role of mantle convection in shaping long-wavelength topography.

scholarly journals On the Scales of Dynamic Topography in Whole-Mantle Convection Models

2018 ◽  
Vol 19 (9) ◽  
pp. 3140-3163 ◽  
Author(s):  
M. Arnould ◽  
N. Coltice ◽  
N. Flament ◽  
V. Seigneur ◽  
R. D. Müller
Keyword(s):  
Mantle Convection ◽  
Dynamic Topography

Dynamic Topography Change of the Eastern United States Since 3 Million Years Ago

Science ◽  
2013 ◽  
Vol 340 (6140) ◽  
pp. 1560-1563 ◽  
Author(s):  
David B. Rowley ◽  
Alessandro M. Forte ◽  
Robert Moucha ◽  
Jerry X. Mitrovica ◽  
Nathan A. Simmons ◽  
...  
Keyword(s):  
Sea Level ◽  
Coastal Plain ◽  
Mantle Convection ◽  
Sedimentary Rocks ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Eastern United States ◽  
Dynamic Topography ◽  
Isostatic Adjustment ◽  
Global Sea Level

Sedimentary rocks from Virginia through Florida record marine flooding during the mid-Pliocene. Several wave-cut scarps that at the time of deposition would have been horizontal are now draped over a warped surface with a maximum variation of 60 meters. We modeled dynamic topography by using mantle convection simulations that predict the amplitude and broad spatial distribution of this distortion. The results imply that dynamic topography and, to a lesser extent, glacial isostatic adjustment account for the current architecture of the coastal plain and proximal shelf. This confounds attempts to use regional stratigraphic relations as references for longer-term sea-level determinations. Inferences of Pliocene global sea-level heights or stability of Antarctic ice sheets therefore cannot be deciphered in the absence of an appropriate mantle dynamic reference frame.

Slab deformation in the Bengal basin due to uplift of the Shillong Plateau and the Indo-Burmese Ranges since the Pliocene, constrained by a Dynamic Topo-Tomographic technique

2020 ◽  
Author(s):  
Raghupratim Rakshit ◽  
Robert James Wasson ◽  
Devojit Bezbaruah
Keyword(s):  
Mantle Convection ◽  
Plate Tectonics ◽  
Bengal Basin ◽  
Dynamic Topography ◽  
Shillong Plateau ◽  
Total Change ◽  
Deep Basin ◽  
The Past ◽  
The North ◽  
Shelf Region

&lt;p&gt;Earth&amp;#8217;s topography is mainly controlled by the structures associated with density differences of the lithosphere and the crust. This is related to isostatic topographic processes which work in association with mantle-induced deformation that together leads to dynamic topography. In this study, the dynamic topographic model of Rubey et al. (2017) has been used. The model links sedimentary basin evolution with plate tectonics and mantle convection to deliver a quantitative framework to understand the combined roles of mantle convection and subduction processes in time and space. Dynamic topography is different from surface topographic variations and this difference can be used to explain past deformation. In the Bengal basin, sedimentation began in a deep basin and shelf region that endured continuous subsidence, and then became involved with crustal adjustments due to collision and uplift of the Himalayas and later on the Indo-Burmese Ranges (IBR). In this study, the dynamic topographic changes have been used to understand the past deformational history and plate dynamics beneath the Bengal Basin and IBR. The model has been run in a cloud-computing environment using the global mantle convection code TERRA along with the plate reconstruction Gplates software to reproduce dynamic topographic variations. In such conditions the shelf zones are the dynamic topographic representation. The results for Bengal basin region, 22.5&amp;#176; to 24.5&amp;#176;N latitude and 91.5&amp;#176; to 93.5&amp;#176; E longitude for the past 20Ma, showed that high sedimentation in the subducting basinal setting caused rising dynamic topography from 20 to 5 Ma continuously. A negative trend (i.e. subsidence) is seen for the past 5Ma. Moreover, when total change in subsidence in the last 5Ma is considered, it has been observed that the northern front of the Bengal Basin steeply plunged towards the north at a time when the Shillong Plateau was uplifted. While there has been overall subsidence of the region both the Shillong Plateau and IBR rose. Present day seismic tomographic study indicates the presence of denser magmatic mass beneath Shillong Plateau which might also be linked with Indian oceanic plate subduction. The Dynamic Topo-Tomographic Model suggests that slab bending associated with subduction caused detachment of the denser material zones and change in the slab setting above which the thick sedimentary column is stacked. The rise of the rigid Shillong Plateau caused a deformational front in the sedimentary zone, south of the Plateau, resulting in a steep plunging dynamic topography.&amp;#160;&lt;/p&gt;

The effect of composite rheology on mantle convection models with plate-like behavior

2020 ◽  
Author(s):  
Maelis Arnould ◽  
Tobias Rolf
Keyword(s):  
Deformation Mechanism ◽  
Mantle Convection ◽  
Plate Tectonics ◽  
Large Scale ◽  
Seismic Anisotropy ◽  
Dislocation Creep ◽  
Diffusion Creep ◽  
Mantle Flow ◽  
Dynamic Topography ◽  
Lattice Preferred Orientation

&lt;p&gt;The coupling between mantle convection and plate tectonics results in mantle flow patterns and properties which can be characterized with different seismic methods. In particular, the presence of mantle seismic anisotropy in the uppermost mantle suggests the existence of mineral Lattice-Preferred Orientation (LPO) caused by asthenospheric flow. Dislocation creep, which implies non-Newtonian mantle rheology, has been identified as a deformation mechanism responsible for such LPO leading to seismic anisotropy. While it has been proposed that the use of a composite rheology (with both diffusion and dislocation creep) significantly impacts the planform of convection and thus the resulting tectonic behavior at the surface, large-scale mantle convection studies have typically assumed diffusion creep (Newtonian rheology) as the only deformation mechanism, due to computational limitations.&lt;/p&gt;&lt;p&gt;Here, we investigate the role of composite rheology on mantle convection with self-consistent plate-like behavior using the code StagYY in 2D annulus (Hernlund and Tackley, 2008). We quantify the spatial distribution of dislocation creep in the mantle in models characterized by different transitional stresses between Newtonian and non-Newtonian rheology. Such models are built on previous viscoplastic cases featuring Earth-like plate velocities, surface heat flow and topography with Newtonian rheology (Arnould et al., 2018). We then investigate how composite rheology impacts the planform of convection and the style of plate-like behavior.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Hernlund, J. W., &amp; Tackley, P. J. (2008). Modeling mantle convection in the spherical annulus. Physics of the Earth and Planetary Interiors, 171(1-4), 48-54.&lt;/p&gt;&lt;p&gt;Arnould, M., Coltice, N., Flament, N., Seigneur, V., &amp; M&amp;#252;ller, R. D. (2018). On the scales of dynamic topography in whole&amp;#8208;mantle convection models. Geochemistry, Geophysics, Geosystems, 19(9), 3140-3163.&lt;/p&gt;

scholarly journals The impact of rheological uncertainty on dynamic topography predictions: Gearing up for dynamic topography models consistent with observations

2019 ◽  
Author(s):  
Ömer F. Bodur ◽  
Patrice F. Rey
Keyword(s):  
Mantle Convection ◽  
Numerical Models ◽  
Mantle Flow ◽  
Dynamic Topography ◽  
Dynamic Component ◽  
Density Anomaly ◽  
Low Viscosity ◽  
Local Reduction ◽  
Non Linear ◽  
The Impact

Abstract. Much effort has been given on extracting the dynamic component of the Earth’s topography, which is driven by density heterogeneities in the mantle. Seismically mapped density anomalies have been used as an input into mantle convection models to predict the present-day mantle flow and stresses applied on the Earth’s surface, resulting in dynamic topography. However, mantle convection models give dynamic topographies generally larger by a factor of ∼2 compared to dynamic topographies estimated from residual topography after extraction of the isostatically compensated topography. Our 3D thermo-mechanical numerical experiments suggest that this discrepancy can be explained by the use of a viscosity model, which doesn’t account for non-linear viscosity behaviour. In this paper, we numerically model the dynamic topography induced by a spherical density anomaly embedded into the mantle. When we use non-linear viscosities, our numerical models predict dynamic topographies lesser by a factor of ∼2 than those derived from numerical models using isoviscous rheology. This reduction in dynamic topography is explained by either the formation of a low viscosity channel beneath the lithosphere, or a decrease in thickness of the mechanical lithosphere due to induced local reduction in viscosity. Furthermore, we show that uncertainties related to activation volume and fluid activity, lead to variations in dynamic topography of about 20 %.

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