Why do intracontinental basins subside longer?

Why do intracontinental-GeologyPage
Why do intracontinental basins subside longer? 3D model of an intracontinental basin Credit: GFZ

Intracontinental basins like the North German Basin, the West Siberian Basin, the Barents Sea or the Congo Basin are large depressions of the Earth’s surface. How these basins initially start to form and why they subside over hundreds of millions of years at very slow rates – far longer than continental margins or foreland basins next to mountain chains – has so far not been explained with a general concept. Scientists from the GFZ section Basin Modelling have reevaluated the nature of the subsidence history of intracontinental basins and propose a new overall mechanism to explain the subsidence of these basins.

Intracontinental basins form in the interior of continents, far away from active plate boundaries. Initial significant extensional spreading events caused by plate tectonic activities can thereby be ruled out as an explanation. Why the basins form and subside continuously on a long term base remained enigmatic for a long time. These basins all share an enormous preservation potential and are therefore regarded by geoscientists as important archives to explore both the geodynamic history of the Earth and the geo-resources the basins contain. Dr. Mauro Cacace and Prof. Magdalena Scheck-Wenderoth, Head of the GFZ section Basin Modelling, now showed, based on 3-D thermomechanical numerical simulations, how the basins evolve in response to small to moderate extension caused by a thermal anomaly.

In a study published in the Journal of Geophysical Research Solid Earth they show that re-equilibration processes take place within the basins over geological time spans, between surface processes caused by sedimentation and thermal tension, caused by slow cooling of the deep lithosphere plate. The interplay of these equilibration processes causes variations in the strength of the plate that can explain for the subsidence. Dr. Cacace: “Intracontinental basins are dynamic systems that do not attain a state of isostatic equilibrium. The continuous subsidence can be explained by the striving for a thermal and mechanical equilibrium that is never reached”. The formation of intercontinental basins can only be explained by considering all these processes and their interdependence under proper temporal and spatial scales.


Reference:
Cacace, M., and M. Scheck-Wenderoth (2016), Why intracontinental basins subside longer: 3-D feedback effects of lithospheric cooling and sedimentation on the flexural strength of the lithosphere, Journal of Geophysical Research – Solid Earth, 121, DOI: 10.1002/2015JB012682.

Note: The above post is reprinted from materials provided by GFZ German Research Centre for Geosciences.

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