Integrated multi-proxy source-to-sink analysis of the Lower Cretaceous of the Essaouira-Agadir Basin.

Abstract

This study investigates the Provenance of the Barremian-Aptian fluvial clastics exposed in the Essaouira-Agadir Basin which bears an important potential in terms of offshore feeding of reservoir sands. Thin section petrography and SEM, heavy minerals analysis, and detrital zircon dating were conducted and integrated with a large dataset of published low-temperature thermochronology studies to model the associated source-to-sink system. The homogeneity of fingerprints throughout the basin indicated a single provenance for both the northern and southern studied transects. The hinterland analysis based on LTT data revealed that only the Western Meseta and MAM regions were possible source candidates for the Barremian Aptian which was confirmed by detrital zircon geochronology. Heavy mineral populations confirmed that sediment sources were of recycled nature and rock fragment populations in the EAB revealed clasts of limestones, sandstones and volcanic nature only matching with the MAM. The Barremian-Aptian fluvial being sourced from a source-tosink system of moderate size (200-300 km long) with an exclusive or dominant source located in the MAM (western High Atlas) provides the best fit explanation matching with each individual dataset. This likely provided a sand-rich mix of sediment resulting from the erosion of Triassic continental basins, with associated clays resulting from the weathering of basalts and Triassic /Jurassic mudstones. EarthArXiv preprint3 Associated low sea level allowed the direct sediment supply within the slope/offshore domain where seismic imaging suggests the presence of synchronous high reflectivity deep-water channels located in structural lows controlled by diapiric salt movement. An overall NNW drainage deflection is observed offshore the northern part of the basin. The Mesetian domain is likely to be undergoing denudation at the same time and shedding a clastic-rich sediment supply north of the studied region.Due to the offshore NNW deflection of the sediment supply along the northern part of the EAB, mixing between MAM and Mesetian sands is likely offshore Essaouira making the probability of good reservoir sands in the region high.

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

“…This complex uplift history, which began with inversion of Palaeozoic basin within the Carboniferous Variscan orogenic cycle, led to formation, filling, exhumation and erosion of sedimentary sinks across north‐west Gondwana, triggering recycling of significant volumes of sediment across the Gondwana shelf and subsequent homogenisation of the zircon record, a process recorded in other sediment proxies. When studied, sediment geochemistry, petrography and heavy mineral analysis indicate sedimentary reworking as a key process during both Palaeozoic and Mesozoic times (Figure 8) (Accotto et al, 2019; Gärtner et al, 2017; Ghienne et al, 2018; Roquette et al, 2021).…”

“…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. However, outside of Permian samples from the High Atlas of Morocco (Perez et al, 2019), no such shift is observed in the detrital zircon U–Pb geochronology record (Azdimousa et al, 2019; Domènech et al, 2018; Roquette et al, 2021).…”