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Abstract
We present a series of 2D thermo-mechanical numerical experiments of thick-skinned crustal extension including a pre-rift salt horizon and subsequent thin-, thick-skinned, or mixed styles of convergence accompanied by surface processes. Extension localization along steep basement faults produces half-graben structures and leads to variations in the original distribution of pre-rift salt. Thick-skinned extension rate and salt rheology control hanging wall accommodation space as well as the locus and timing of minibasin grounding. Upon shortening, extension-related basement steps hinder forward propagation of evolving shallow thrust systems; conversely, if full basin inversion takes place along every individual fault, the regional salt layer is placed back to its pre-extensional configuration, constituting a regionally continuous décollement. Continued shortening and basement involvement deform the shallow fold-thrust structures and locally breaches the shallow décollement. We aim at obtaining a series of structural, stratigraphic and kinematic templates of fold-and-thrust belts involving rift basins with an intervening pre-rift salt horizon. Numerical results are compared to natural cases of salt-related inversion tectonics to better understand their structural evolution.
Highlights
It is well known that the inherited structural framework and the distribution of décollement-prone units have a strong influence on the structural style of fold-and-thrust belts and their kinematic evolution (Ruh et al, 2012; Granado et al, 2016; Lacombe and Bellahsen, 2016; Tavani et al, 2021)
A total of nine numerical experiments are conducted to test the effects of the rate of extension (1 vs. 8 mm/yr), the rheology of the salt horizon, and the style of shortening on the resulting sedimentary architectures and structural styles of inverted basement half-graben systems (Table 2) with a pre-rift salt horizon
Finite-difference 2D thermo-mechanical numerical experiments have been carried out to model the formation of extensional basins with a pre-rift salt layer to be subsequently shortened by thin, thick-skinned, and thin- to thick-skinned convergence coeval with surface processes
Summary
It is well known that the inherited structural framework and the distribution of décollement-prone units have a strong influence on the structural style of fold-and-thrust belts and their kinematic evolution (Ruh et al, 2012; Granado et al, 2016; Lacombe and Bellahsen, 2016; Tavani et al, 2021). Salt tectonics concepts have been more recently incorporated and provide key concepts in terms of related geometries and kinematics (see Jackson and Hudec, 2017 for a recent thorough review), when early salt structures become involved in the thrust wedge (e.g., Rowan and Vendeville, 2006; Jahani et al, 2007; Callot et al, 2012; Callot et al, 2012; Duffy et al, 2018; Granado et al, 2019; Célini et al, 2020). Salt is well known for being an extremely efficient décollement (Davis and Engelder, 1985), whose inherent weakness allows for relatively fast flow at geological rates in response to load. Wellconstrained natural examples may show characteristics at odds with the mechanical behavior of salt proposed from laboratory experiments (Li and Urai, 2012)
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