Identifying local vs. regional drainage using multiproxy provenance tracers – Tracking the Moroccan Late Triassic fluvial system

Abstract

The Kerrouchen Basin is an understudied rift basin in the Middle Atlas of Morocco, where over 600 m of Triassic stratigraphy is well exposed. It was partially inverted during the Atlasic orogeny whilst preserving the original basin geometry. Within the Kerrouchen Basin, two distinct fluvial systems are present. The first, recorded by the K3 Formation, is a braided-meandering fluvial system showing vertical and lateral amalgamation. The K3 is an axial fluvial system that shows a predominant drainage direction towards the north-north-east, parallel to the rift zone axis, ultimately draining towards the Tethys Ocean. The K4 Formation records a secondary, Tributary Fluvial System (TFS), with facies spanning a range of alluvial-fluvial processes. Paleoflows predominantly record drainage to the SSW, transverse to the basin axis.Heavy mineral and petrographic analysis of the two fluvial systems indicates two distinct sedimentary provenances for the depositional system. The K3 system records a higher proportion of sediment sourced from igneous rocks. In contrast, the K4 system records a local provenance signal derived from adjacent low-medium grade metamorphic terranes exposed to the east. Comparison of the provenance and stratigraphic trends within the Kerrouchen Basin with work undertaken in the Central and Western High Atlas suggests a shared source region for the through going axial fluvial systems recorded in the High Atlas and Kerrouchen basins. Our study provides evidence for a linked fluvial system spanning the High and Middle Atlas rifts during the Triassic, indicating that a regional fluvial system was present within Central Pangea from Middle-Late Triassic times. Identifying regional and local drainage networks within the Triassic rift basins has key implications for paleogeographic reconstructions and future exploration efforts for hydrocarbons and CCS sites within Morocco.