the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Selective inversion of rift basins in lithospheric-scale analogue experiments
Weronika Gorczyk
Timothy Chris Schmid
Peter Graham Betts
Alexander Ramsay Cruden
Eleanor Morton
Fatemeh Amirpoorsaeed
Abstract. Basin inversion is commonly attributed to the reverse reactivation of normal basin-bounding faults. This association implies that basin uplift and inversion-related structures are mainly controlled by the frictional behaviour of pre-existing faults and associated damage zones. In this study, we use lithospheric-scale analogue experiments of orthogonal extension followed by shortening to explore how the flow behaviour of ductile layers underneath rift basins promote or suppress basin inversion. Our experiments show that the rheology of the ductile lower crust and lithospheric mantle, modulated by the imposed bulk strain rate, determine: (1) basin distribution in a wide rift setting and (2) strain accommodation by fault reactivation and basin uplift during subsequent shortening. When the ductile layers deformed uniformly during extension (i.e., stretching) and shortening (i.e., thickening), all of the basins were inverted. When viscous deformation was localised during extension (i.e., necking) and shortening (i.e., folding), only some basins – which were evenly spaced apart – were inverted. We interpret this selective basin inversion to be related to the superposition of crustal-scale and lithospheric-scale boudinage during the previous basin-forming extensional phase.
Anindita Samsu et al.
Status: open (until 02 May 2023)
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RC1: 'Comment on egusphere-2023-411', Anouk Beniest, 17 Mar 2023
reply
This paper discusses the results of analogue experiments that simulate basin inversion after extension. The focus is on the behavior of the ductile lower crust when basins invert. The authors find that depending on the strength (rheology) of the ductile layer and mantle basins form in a wide rift setting and are only all inverted when initial basin distribution was evenly spaced. In case of localized extension and shortening only some basins invert and become uplifted. This uplift then occurs at regular intervals.
The focus of this study on the behavior of the ductile lower crust in basin inversion helps us to understand the dynamics behind basin inversion at crustal scale. The methods used are well-established. The focus of their study is unique and the conclusions reached are substantial and lead to more detailed questions beyond the scope of this paper, for example: what influences the wavelength of basin formation and basin inversion?
I think the paper is well-written and well-structured and it advances our understanding of how the ductile lower crust behaves under changing tectonic stress fields. I would like to congratulate the authors with their work and I recommend this work for publication, with only some technical corrections.
With kind regards,
Anouk Beniest
Assistant Professor, Vrije Universiteit Amsterdam
Technical corrections:
- In the caption of figure 1 you refer to the liquid asthenosphere as ‘a fluid asthenosphere’. I suggest to replace ‘fluid’ by ‘liquid’ (i.e. ‘a liquid asthenosphere’), also in other parts of the text: liquid describes a state of matter (‘liquid [state] asthenosphere [matter]’), whereas a fluid refers to any substance that flows.
- In figure 2, the red arrows that indicate the direction of movement are placed parallel along the long side of the model box. I was a bit confused by that, thinking that extension/shortening was imposed on the side walls only. Maybe consider replacing the arrow left or right to the moving arm in the picture, on perpendicular to the short side of the model box.
- Line 225: a graben is defined as a ‘depressed area’. I understand what you mean, but it reads as if the graben is very sad. Maybe just write ‘depressions [or topographic depressions] that are bounded by parallel normal faults’.
- Line 256: ‘Fault traces are smoother…’What exactly do you mean with smoother? Are they continuous? Less edgy? Longer/shorter? Can you be more specific/descriptive?
- Line 260: you mention de words ‘northernmost’ and ‘southernmost’. Can you maybe indicate what’s north and south to you on the figure? Or maybe use top vs bottom, or use some other reference indicator (A - A', B - B', or something else)?
- Line 383: ‘… inversion is localized in the center of the basin…’ It is not entirely clear to me if you observe as well that, despite your models being isothermal, the inversion localizes at the center of the basin. Or are you just making the point here that, despite your model being isothermal, the inverted basins are also thinnest in center of the basin, possibly due to isostatic readjustment, hence this would correspond to a higher heat flow? Is the expected higher heat flow in that case a result of the large wavelength thinning of the lithosphere and isostatic equilibration of the thinned regions, or do you still think that the thermal structure is of importance for the location of basin inversion? I think this is a very interesting point that you are making, so could you maybe elaborate a bit more on the consequences of lithosphere thinning on the potential changes in heat flow?
Citation: https://doi.org/10.5194/egusphere-2023-411-RC1
Anindita Samsu et al.
Anindita Samsu et al.
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