Control of inherited accreted lithospheric heterogeneity on the architecture and the low, long-term subsidence rate of intracratonic basins

Abstract

Intracratonic basins tend to subside much longer than the timescale predicted by thermal relaxation of the lithosphere. Many hypotheses have been suggested to explain their longevity, yet few have been tested using quantitative thermo-mechanical numerical models, which capture the dynamic of the lithosphere. Lithospheric scale geodynamic modelling preserving the tectono-stratigraphic architecture of these basins is challenging because they display only few kilometres of subsidence over 1000 of km during time periods exceeding 250 Myr. Here we present simulations that are designed to examine the relative role of thermal anomaly, tectonics and heterogeneity of the lithosphere on the dynamics of intracratonic basins. Our results demonstrate that initial heterogeneity of accretionary continental lithosphere explains long-term subsidence and the arches-basins architecture of Saharan type intracratonic basins at first order. The simulations show that initially warm and heterogeneous lithospheres inherited from accretion are strong enough to resist local isostatic re-equilibration for very long period of time. Indeed, the lateral density variations store potential gravitational energy that is then slowly dissipated by differential erosion and slow vertical movements. For relatively well-accepted coefficient of erosion of 10-6 m2/s, the subsidence last longer than 250 Myr. Extensional tectonic forcing and thermal anomalies both results in an effective strength drop of the lithosphere, which allows a temporarily acceleration of local isostatic re-equilibration. Periodic changes in far field tectonic forcing from extension to compression complicate the tectono-stratigraphic architecture (intra-basin arches, sub-basins) introducing stratigraphic unconformities between different neighbouring basins such as the ones observed in North Africa.

Effects of multi-extensional tectonics in a cratonic area: 3D numerical modeling and implications for the Congo Basin

“…The succession of compressional events to a rift extension occurred also in other ICBs, such as those of North America, (e.g., Klein and Hsui, 1987) and Australia, where the phases of intracontinental orogeny lead to the separation of the Centralian Superbasin of Australia in four main basins (Officer, Amadeus, Ngalia and Georgina basins), between 600 and 300 Myr (e.g., Lindsay, 2002). It has been demonstrated that small variations of the far field stresses cause period of subsidence acceleration, deceleration and even inversion (Perron et al, 2020). Therefore, periodic changes in far field tectonic can significantly complicate the tectono-stratigraphic architecture of the basins, by introducing stratigraphic unconformities between different neighboring basins.…”

“…In particular, the modelled fields, depending on the topography and density variations, induced by the mantle upwelling, could reproduce a trend of anomalies similar to that observed, but not the shape of all the small anomalies related to the sediments distribution and local heterogeneities of the basement, present already before the syn-rift phase or acquired during the following tectonic events. The basement heterogeneity can have played a significant role on the long-term subsidence of the ICBs, by resisting local isostatic re-equilibration (Perron et al, 2020) and thus should be included in the future numerical models to reproduce the short wave-length of the basement depth variations.…”

“…These contain the memory of the processes that are responsible for the past deformations and are readily available in intracratonic basins (ICBs). Different hypotheses (e.g., lithospheric stretching and subsequent thermal contraction, crustal and mantle phase changes, changes in the intraplate stress field, convective instabilities in the mantle, inherited heterogeneities) attempted to explain the long-lasting subsidence of these basins, characterized by prolonged intervals of low rate subsidence, alternating with episodic accelerations in subsidence rates (e.g., Klein and Hsui, 1987;Burke and Gunnell, 2008, Downey and Gurnis, 2009, Crosby et al, 2010, Allen and Armitage, 2012Perron et al, 2020). However, several ICBs originated from one or more rift phases, such as the Parnaiba basin (de Wit and and the basins of north-central Africa (e.g., Burke and Gunnell, 2008).…”

The Ordovician strata of the Ennedi Plateau, northeastern Chad (Erdi Basin)

“…Interestingly, the Peninsula Sandstone characterizes a proximal setting where the succession wedge-out onto basement rocks at the scale of a few tens of km, as should also occurred to the south of the Ennedi. Note that the relatively limited thickness (<200 m) of the Ordovician in the study area might not be solely a signature of the proximality of the Ennedi, as along-strike thickness changes reflecting subsidence/uplift trends controlled by basement heterogeneities [Nkono et al, 2018] could also have played a significant role, as recognized elsewhere throughout the platform [Klitzsch, 1970, Perron et al, 2021.…”

Control of Hercynian Orogeny on basin evolution on the southern margin of the Tethyan region: A review and new insights

“…And therefore, tectonic events in North Africa and Middle East during this period were probably independent of the Caledonian Orogeny. Instead, the origins of the Late Silurian event and related low uplift within the African basins were interpreted as the result of the following: (1) intra‐plate stress linked to far‐field stresses (Perron, 2019), which is probably from the collision front of Iapetus Ocean closure (Fekirine & Abdallah, 1998) or rifting along the Gondwana margin (Boote & Clark‐Lowes, 1998); and (2) heterogeneity of accretionary continental lithosphere equilibration together with periodic changes in far‐field tectonic forcing from extension to compression (Perron et al, 2021).…”