Ordovician stratigraphy and benthic community replacements in the eastern Anti-Atlas, Morocco

Abstract The Anti-Atlas contains a thick, volcanic-free Ordovician succession that originally deposited in passive-margin basin. Three main sedimentary packages are bounded by major unconformities: (i) the Tremadocian–Floian Lower Fezouata and Upper formations, which unconformably overlie palaeorelief of Cambrian rifting volcanosedimentary complexes, subsequently topped Dapingian paraconformable gap; (ii) Darriwilian–Katian Tachilla Formation First Bani Ktaoua groups, latter overlain Hirnantian glaciogenic succession; (iii) Second Group, infilled former palaeorelief. Due to scarcity carbonate interbeds for etching analyses, leading rare references conodonts, global chart is interpolated on basis microphytoplancton (acritarchs chitinozoans), regional graptolites brachiopods. counter-clockwise rotation Gondwana led its Moroccan margin from mid- high-latitude positions, onset siliciclastic, wave- storm-dominated platform. Flooding surfaces marked shelly silty reflect episodic development echinoderm–bryozoan meadows during Katian times; areas protected siliciclastic input, they reached massive bedded bioaccumulations (Khabt-el-Hajar Formation). glaciation controlled incision numerous tunnel channels, with both alluvial fluvial sediments glaciomarine diamictites. was definitively sealed Silurian times.