The Lower Ordovician Fezouata Konservat-Lagerstätte from southern Morocco has been one of the major palaeontological discoveries of the last decade. It provides a unique insight into one of the most critical periods in the evolution of marine life: the Cambrian-Ordovician transition. However, its potential for deciphering key trends in animal diversification was hitherto largely limited by major uncertainties concerning its stratigraphic position, age and environmental setting. Based on extensive fieldwork, fossil evidence, and facies recognition, our study provides clarification on these three crucial issues. Exceptional preservation is limited to two intervals within the Fezouata Shale. Graptolites indicate a late Tremadocian age for the Fezouata Konservat-Lagerstätte as a whole, which is supported by biostratigraphical evidence provided by acritarchs. Sedimentological features and reconstructed patterns of relative sea-level changes indicate relatively shallow-water environmental conditions, under distal storm influence, in an offshore to lower shoreface siliciclastic ramp setting. The Fezouata Biota represents a unique and exceptional window into the palaeobiodiversity in open-marine conditions, thus contrasting with the other Ordovician Konservat-Lagerstätten presently known. In our analyses of this new set of data, we pave the way for accurate temporal, faunal and environmental comparisons with other Lower Palaeozoic Konservat-Lagerstätten, and unlock the full potential of the Fezouata Biota to better understand the processes and scenarios of early animal radiations.

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Seven sections, covering the upper Albian to lowermost Turonian, have been correlated from full-marine to continental-dominated deposits across a passive margin, along a transect 425 km long, from the present-day Atlantic coast to the "Pre-African Trough" between the Anti-Atlas and the HighAtlas. The thickness of the Cenomanian succession changes from around 500 metres in the fully marine sections to 250 metres in mostly continental facies in the western High-Atlas, about 150 km updip, to a few tens of metres in the Bou Tazoult area. The strata thicken again eastwards into the Pre-African Trough where they can be traced without major facies changes to the Kem Kem embayment and to the Bechar area in Algeria. Over all this eastern area, continental facies are overlain by the fully-marine shallow-water deposits of the Cenomanian-Turonian boundary interval. A first major conclusion is that fluvial aggradation in high-frequency transgressive-regressive sequences is coeval with the seaward-shift of the shoreline, in accordance with the genetic sequence stratigraphic model of GALLOWAY (1989). Both the flatness of the depositional profile and the corresponding very low energy of the marine environment during the transgressions account for the blanket of red continental clays on top of marine facies in updip depositional sequences, which is then preserved under the marine transgressive surface of the next sequence. Carnets Geol. 15 (12)A second major conclusion is that the high-frequency transgressive-regressive (T-R) sequences do not look like classical parasequences bounded by transgression surfaces. They usually exhibit a surface created by a sea-level fall within the regressive half-cycle. This is interpreted in the following way: regressions did not operate through a regular seaward-shift of the shoreline, but through stepped sealevel falls. The very low slope of the depositional ramp is thought to have enhanced the sequence stratigraphic record of such stepped regressions. Short-term, high-frequency sequences are organized into medium-frequency T-R sequences (seven in the Cenomanian) which show an overall aggrading and slowly retrograding pattern along the whole transect.Comparisons with other basins show that medium-frequency sequences do not fit the third-order depositional sequences described elsewhere, casting doubts about a eustatic mechanism for their deposition. Tazoult), sur environ 250 km. La série s'épaissit à nouveau vers l'est dans le sillon pré-africain où elle peut être suivie sans changements notables vers le golfe des Kem-Kem et le secteur de Béchar en Algérie. Sur toute la partie orientale de la transversale, les faciès continentaux ou mixtes sont recouverts par les dolomies marines du passage Cénomanien-Turonien. Une première conclusion majeure est que, dans les séquences transgression-régression (T-R) à haute fréquence, l'aggradation fluviatile accompagne sans hiatus le déplacement de la ligne de rivage au cours du demi-cycle régressif, en accord avec le modèle génétique de GALLOWAY (...

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23The Essaouira-Agadir Basin (EAB) of Morocco contains the most extensive exposure of 24 Aptian to Lower Albian strata onshore the NW African Atlantic Margin. This paper documents the 25 first high-resolution, multi-disciplinary stratigraphic approach for the Aptian to Lower Albian on the 26 NW African Atlantic Margin. Previous biostratigraphic work almost exclusively relied on long-27 distance correlation of ammonoids to the Mediterranean -Caucasian Realm. Recent biostratigraphic 28 work has questioned some of the previous interpretations, highlighting significant faunal endemism 29 and complications with correlation to other key Aptian sections. 30This study focuses on 5 key sections: Tiskatine, Id Amran, Assaka, and DSDP 416/370. 31Distribution of ammonoids, foraminifera, and calcareous nannofossils are reported from a bed-by-32 bed collection made at Tiskatine. 33The analysis of foraminiferal and calcareous nannofossil assemblages enable correlation to 34 standard zonation schemes; but also highlights the urgent need of revision and future work on the 35 integration of these schemes across disciplines. The study, further, includes δ 13 Ccarb, δ 13 Corg, and total 36 organic carbon (TOC) data that is compared to reference material from the Vocontian Basin. 37The combined litho-, bio-, chemo-, and sequence stratigraphic analysis establishes a robust 38 chronostratigraphic framework for regional and super-regional correlations and a type section is 39 proposed for the Aptian of NW Africa at Tiskatine. 40 41