Low-temperature thermochronology as a control on vertical movements for semi-quantitative Source-to-Sink analysis: A case study for the Permian to Neogene of Morocco and surroundings

Abstract

Continental passive margins and their hinterlands in the Atlantic realm are the locus of a significant amount of studies that evidence pre-, syn-, and post-rift episodic km-scale exhumation and burial episodes. We submit a 3-steps workflow to obtain 1) exhumation/burial rates, 2) eroded material flux, and 3) paleoreconstructions of source and sink domains. We apply this workflow in onshore NWAfrica from Permian to the Present-day.Our synthesis of available time-Temperature (t-T) modelling results predicts high exhumation rates in the Anti-Atlas (0.1 km/Myr) during the Early to Middle Jurassic, and in the High Atlas (0.1 km/Myr) and Rif (up to 0.5 km/Myr) during the Neogene. These rates are comparable to values typical of rift flank, domal or structural uplifts settings. During the other investigated periods, exhumation rates in the Meseta, High-Atlas, Anti-Atlas, and Reguibat shield are around 0.04±0.02 km/Myr. The exhumation rates are then used for interpolation at the regional scale, in order to subsequently calculate the volume of rocks eroded during the exhumation episodes. Estimates of eroded material fluxes are between 0.2x10^3 and 7.5x10^3 km3 (in the Meseta and the Reguibat Shield, respectively). Ten erosional (quantitative, from interpolation results) and depositional (qualitative, from data synthesis) “source-and-sink” maps have been constructed. Emphasis is placed on the Jurassic and Cretaceous periods comprising six source-and-sink maps. The maps are based on the extent of exhumed domains, geological maps, lithofacies from onshore and offshore basins, biostratigraphic data, new geological fieldwork, and well data. The results illustrate changes in the source-to-sink systems and allow for a better understanding of the Central Atlantic margin hinterlands evolution.

‘I hate sand … it gets everywhere’—Phanerozoic sedimentary recycling from NW Africa

“…The older samples, Cambrian through Neoproterozoic, contain high levels of Eburnean and late Pan‐African (WAC Cadomian stage) grains, due to their deposition prior to the formation or exposure of Pan‐African zircons within the source regions of these depositional systems. A Triassic sample with elevated Eburnean zircon populations, identified as noise, could record erosion from the pre‐Pan‐African strata in the Western Anti‐Atlas as suggested by multiple source to sink studies (Charton et al, 2021; Domènech et al, 2016, 2018; Gouiza et al, 2017).…”

“…The onset of compressional tectonics from the north and west during the Variscan orogeny and formation of the Pangea supercontinent led to progressive shallowing and eventual exposure of the Western Meseta and north of the Eastern Meseta, alongside significant Variscan magmatism north of the Anti‐Atlas (Figures 1 and 3) (Accotto et al, 2020; Hoepffner et al, 2006). During the Permian, the Meseta formed a key source region (Charton et al, 2021), evidenced by the abundance of Variscan cycle grains within the Permian sediments of the High Atlas (Perez et al, 2019).…”

“…Following the eruption of the CAMP basalts at the Triassic–Jurassic boundary, a series of lower Jurassic marginal marine gulfs developed, with initial deposition dominated by terrigenous and marginal marine sedimentation prior to the development of carbonate platforms and mixed carbonate–clastic systems during the Middle Jurassic, coeval with exhumation of Palaeozoic massifs within Morocco (Bertotti & Gouiza, 2012; Carr, 2003; Charton et al, 2018, 2021; Davison, 2005; Duval‐Arnould et al, 2021; Gouiza et al, 2017, 2019; Guiraud et al, 2005; Laville et al, 2004).…”

“…Furthermore, the source and scale of Mesozoic and Cenozoic sedimentary systems of north‐west Africa is unclear. Source regions do change in the Mesozoic and Cenozoic—for example the Anti‐Atlas and Reguibat shield were source regions in the Triassic–Lower Jurassic times but not in the Upper Jurassic, where the Moroccan Meseta became a source (Barbero et al, 2007, 2011; Charton et al, 2018, 2021; Gouiza et al, 2017; Pratt et al, 2016; Saddiqi et al, 2009). This should, based on basement geology, see a shift in provenance from Eburnean and Pan‐African grains, to Pan‐African and Variscan grains with accessory Eburnean grains.…”

“…North‐west Africa has been the subject of numerous detrital zircon studies, which have found detrital zircon populations typical of north‐west African basement, indicating provenance from the West African Craton (WAC) and Moroccan Meseta (Figure 1). However, recent Mesozoic thermochronology studies show that significant shifts in source regions occurred, which detrital zircon studies do not seem to capture (Charton et al, 2021), with the exception of a shift record between the Permian and Triassic units of the High Atlas (Perez et al, 2019). To address this discrepancy, this study has collected previously published detrital zircon sample data from numerous studies of sediments spanning the last 1000 Ma from the Moroccan segment of the WAC margin and performed a multi‐sample statistical comparison on the data set, to identify the detrital signature of the shifts in source region.…”