Linking Gravity Gradient Inversion with Seismological Regionalization - Implications for the Crustal Thickness of Western Gondwana Cratons
Abstract
We developed a novel inverse scheme, where we invert satellite gravity gradient data for crustal thickness under consideration of regional varying density contrasts between crust and mantle. The inversion is linearized and solved with the Gauss-Newton algorithm and is capable of inverting any gravitational component by the usage of tesseroids for forward calculation. The density contrast is based on seismological regionalization of dispersion curves.
First, we calculate the crustal thickness separately for Amazonia and West Africa. The crustal thickness shows significant differences between the cratons and their surroundings, as well as heterogeneities inside the cratons. In the second step, we calculate the crustal thickness for the reconstructed cratons of Amazonia and West Africa in a Gondwana framework. This requires a geometrical rotation of gravity and seismological data back in time, which is done with the software GPlates. We compute a gravitational field, which removes artificial signals and only accounts for continental masses of the supercontinent. The artificial signal arises from far-field gravity effects of the oceans and contributions from the lithosphere. The latter are calculated from overlapping continent-ocean boundaries (COBs), which can be interpreted as the remnant signal of lithospheric mass loss since the initial stage of rifting. We term the residual gravitational field "Paleo-gravity". Using Paleo-gravity as initial data for the inversion, we are able to study the Moho depth of Western Gondwana ("Paleo-Moho"). Paleo-gravity and Paleo-Moho help to get a more precise view on the anomalies connecting the cratons. Especially the anomalies in the interface of both continents show a smooth signal, which cannot be identified by rotated fields only. Our approach can be applied to other overlapping COBs of Gondwana. Extending this approach to full Gondwana assembly, Paleo-gravity and Paleo-Moho can be used as a tool to understand the tectonic evolution not only of Amazonia and West Africa, but also of the whole supercontinent.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T42D..04H
- Keywords:
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- 1525 Paleomagnetism applied to tectonics: regional;
- global;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 8121 Dynamics: convection currents;
- and mantle plumes;
- TECTONOPHYSICS;
- 8157 Plate motions: past;
- TECTONOPHYSICS;
- 8178 Tectonics and magmatism;
- TECTONOPHYSICS