Bioclastic bottom‐current deposits of a Devonian contourite terrace: Facies variability and depositional architecture (Tafilalt Platform, Morocco)

The study examines bioclastic carbonate contourites that arise from the broad spectrum of bottom-current related sedimentary processes ranging deposition to erosion. result intermittent accumulation sediment are thin and condensed successions with abundant hiatuses. Such deposits poorly known, since broadly accepted contourite-facies model, bi-gradational sequence, characterizes environments contourite depositional systems as a continuous accretion fine-grained siliciclastic sediments. To increase current understanding facies within hiatal records, Eifelian–Frasnian Tafilalt Platform in Morocco was investigated. succession is divided into five associations interpreted reflect pelagic sedimentation bottom currents on terrace, gently inclined section upper slope Gondwana shaped by water-mass interface. Contourite mainly controlled oxic clear-water (documented moderately completely bioturbated limestones hydrogenetic ferromanganese nodules, low organic-carbon contents), at times also an anoxic water mass (featured organic-rich coquinas absent sparse bioturbation predominantly syngenetic framboidal pyrites). Biostratigraphic data overall architecture display palaeoceanographic hydrodynamic associated shifting inner terrace characterized alongslope channel small mounded drift its downslope margin. Energetic furthermore caused abraded surfaces, i.e. plain areas non-deposition localized erosion, sandy condensation layers. microfacies reflects repeated alternation between suspension deposition, winnowing fines, bedload traction, dynamic bypassing reworking, together concomitant seafloor cementation. Coquinas planktonic nektonic organisms identified integral parts sequences showing inverse normal grading. Hiatal lag concentrations intraclasts, nodules conodonts often drape hardgrounds erosional surfaces midpoint these frequently incomplete sequences. This Devonian case provides opportunity investigate spatial temporal variability bed-scale regard drift-scale architecture. In addition, high-resolution record starting point for unravelling pattern oceanic circulation greenhouse world.