Late Triassic ichnoassemblage from a playa-lake system of the Coastal Meseta, Morocco: Palaeoenvironmental and palaeoecological implications

Abstract

Here we present the first comprehensive ichnotaxonomic analysis of a Late Triassic playa system from the Sidi Saïd Maachou Basin, Coastal Meseta (Western Meseta, Morocco). The Late Triassic deposits consist of sediments deposited in various nonmarine environments dominated by dry red-bed facies. These deposits yielded, so far, an ichnoassemblage consisting of the invertebrate ichnogenera Cochlichnus, Cruziana, Diplichnites, Rusophycus, Palaeophycus, and Taenidium associated with the tetrapod tracks Brachychirotherium and Rhynchosauroides. These invertebrate and vertebrate trace fossils are preserved in concave epirelief and convex hyporelief on upper and lower surfaces of laminated mudstones and fine-grained sandstones. The invertebrate ichnofossils were probably made subaqueously and indicate different behaviours of the tracemakers: walking (cursichnium, Acripes), resting (cubichnium, Rusophycus) and combined locomotion-feeding or plowing (pascichnium, Cruziana). Additionally, many other fossils are collected from the same formation, including plant impressions, rhizoliths and fish scales. The invertebrate ichnoassemblage described herein is referred to the Scoyenia ichnofacies, which indicates opportunistic behaviours in temporarily or periodically inundated nonmarine environments, such as playa systems, floodplains and lake margins. The invertebrate ichnoassemblage reported here is the first well documented from the Sidi Saïd Maachou Basin and the Late Triassic of Morocco in general. The strata have a high potential to yield other ichnoassemblages, therefore further exploration is needed.