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During the Early Jurassic, a group of large, aberrant bivalves called lithiotids proliferated in proximal, shallow marine environments. These lithiotids formed bioherms and extensive biostromes in the western and southern margins of the Tethys Ocean as well as eastern Panthalassa. In the Central High Atlas of Morocco, Pliensbachian and Toarcian (Lower Jurassic) lithiotid and lithiotid-coral reefal deposits occur within carbonate and mixed carbonate/siliciclastic neritic depositional settings. This study describes the stratigraphic distribution, taxonomy, and architecture of these lithiotid-rich deposits. The studied lithiotid and lithiotid-coral deposits from Morocco occur in sheltered, near-shore lagoons along tropical carbonate ramps and platforms. These facies are abundant in upper Pliensbachian strata as well as in the early Toarcian. The persistence and similarity of lithiotid-coral buildups across the stage boundary indicate that these ecosystems were not significantly affected by the Pliensbachian/Toarcian extinction in Morocco (at least, not until the Toarcian Oceanic Anoxic Event). In both the upper Pliensbachian and lower Toarcian, lithiotids (Lithioperna and Cochlearites) are frequently associated with phaceloid corals (Retiophyllia in the Pliensbachian and Phacellophyllia and Archaeosmiliopsis in the Toarcian) and solitary corals (Haimeicyclus and Archaeosmilia) as well as other corals and bivalves (Gervilleioperna, Mytiloperna, Opisoma, and rare megalodontids); however, the spatial distribution of taxa is patchy. The close association of lithiotid bivalves and corals is rarely documented in the literature, and lithiotid-coral reefal deposits are rare. Thus, these Moroccan biostromes and bioherms that record the interaction of corals and lithiotids are of particular scientific importance. Furthermore, multiple generations and successions of lithiotid-coral framestones can be observed in both Pliensbachian and Toarcian strata, which provide insight into the evolution of these communities and their resilience to ecosystem perturbations. Despite the success of lithiotid-coral communities in the Pliensbachian and Toarcian, these ecosystems were decimated by the Toarcian Oceanic Anoxic Event and never recovered.

Standard sequence stratigraphy interpretations are commonly built upon the premise of fairly constant sediment supply, leaving vast uncertainties about sequence architecture and sea-level change recorded during major paleoenvironmental disturbances, usually associated with carbonate productivity collapse and increased siliciclastic sediments supply. During relative sea-level rise, this process is referred to as drowning event. However, drastic collapse of carbonate productivity during relative sea-level drop remains poorly documented. The Pliensbachian/Toarcian boundary in Morocco provides an outstanding example of such a case, referred here to as poisoning event. Using bio-, chemo- and high-resolution sequence stratigraphic approaches on horizontal seismic-scale outcrop data, we characterize the architecture of vertically and laterally mixed siliciclastic/carbonate systems. During poisoning event, the standard sequence Lowstand-Transgressive-Highstand system tracts is altered into Highstand-Transgressive-Falling Stage system tracts with little or no evidence for Highstand deposits. Noteworthy, it is important to note that poisoning and drowning events can be confused together in sedimentary records where the shoreline trajectory cannot be clearly tracked, as it has often been the case in previous Pliensbachian/Toarcian studies. The outcome of this study calls thus for a closer re-examination of other carbonate factory collapse event attributed to drowning events without an unambiguous knowledge of their coeval shoreline trajectory.

The red detrital formations of the Central and Eastern High Atlas of Morocco continue to spark a large scientific debate around their age varying from the middle Jurassic to the upper Cretaceous period . Through this paper, we present the results of lithological correlations of five detailed geological sections, covering the Jurassic–Cretaceous “red beds'' series, measured in the Central High Atlas along the Errachidia–Msemrir transect. These detrital strata are outcropped in syncline basin centres, delimited by raised ridges that are formed by lower and middle Jurassic formations. Important lateral variations of facies and thicknesses occur between the eastern and western parts of the studied transect. In the eastern part of the study area, the “red beds'' can be attributed to three lithostratigraphic formations, two formations that are generally sandstone-rich (Guettioua and Jbel Sidal Formations), separated by a third one which is clay-rich (Iouaridene Formation). In contrast, in the western part, the “red beds'' series is best allocated to the sandstone-rich of the Guettioua Formation. During the deposition of the Jurassic–Cretaceous “red beds”, the Central High Atlas Basin was subjected to important tectonics and salt diapirism events. Hence, the important variation of facies and thickness in the “red beds'' series may be best explained by the geodynamic evolution of the Central High Atlas and its control of the building of differential depositional areas. Together with global sea-level and climatic fluctuation, changes in differentiated local subsidence rate are hence pictured as a major driving parameter for facies and age differentiations between the eastern and western parts of the Central High Atlas Basin.

The Early Bajocian witnessed a global environmental perturbation, characterized by faunal and floral turnovers and a positive carbon isotope excursion. In Italy, this environmental perturbation coincided with an eutrophication event and a carbonate crisis, but this has so far not been adequately reported from other settings, leaving doubt about the extent and nature of these phenomena. In this paper, we are reporting on an extensive neritic carbonate factory demise that occurs in the upper Lower Bajocian of Morocco, more precisely in the upper Propinquans – lower Humphriesianum Zones. This demise coincided with the acme of the global carbon isotope perturbation, recorded by a 3‰ positive carbon isotope excursion in the bulk organic matter of Morocco, but not in the micritic phase, due to the fact that the Moroccan carbonate δ13C record is more sensitive to local rather than global influences. Furthermore, we observe that the Lower Bajocian of Morocco is relatively enriched in arenitic siliciclastic deposits, suggesting increased weathering and nutrient levels along the northwestern margin of Africa during the Early Bajocian. However, comparison with neighboring European basins highlights the non-uniqueness and different timing of the response of shallow-water carbonates to the Early Bajocian environmental perturbations, as some regions present no sign of carbonate factory crisis. Hence, we postulate that local factors were important in mediating the response of neritic carbonate factories to this global environmental perturbation. We notably highlight the role of large Early Bajocian sea-level fluctuation as a trigger for carbonate factory change and demise in Morocco.

Preceding the early Toarcian Oceanic Anoxic Event by similar to 1 Myr, the Pliensbachian-Toarcian boundary event is in many aspects as severe and disturbing for the environment as its better-studied successor. Both events are associated with rapid and pronounced global warming, major faunal and floral turnover, increased hydrological cycling and dramatic collapses of carbonate production. To better characterize the Pliensbachian-Toarcian boundary event, a high-resolution, paired carbonate and organic matter carbon isotope survey of three sections from the Central High Atlas Basin of Morocco has been undertaken. A pronounced negative shift in the carbonate carbon-isotope record, not paralleled by a similar excursion in the organic carbon, can be linked to the collapse of the neritic carbonate factory in the earliest Toarcian. These results show that, contrary to the Toarcian Oceanic Anoxic Event, a rapid and massive injection of C-13-depleted carbon into the atmosphere is not responsible for the environmental perturbations observed during the Pliensbachian-Toarcian boundary event. However, input of isotopically non depleted carbon such as mantle source CO2 into the atmosphere as a potential cause for the Pliensbachian-Toarcian boundary event cannot be excluded. This would most probably be sourced from an early pulse of the Karoo-Ferrar Large Igneous Province. (C) 2015 Elsevier Ltd. All rights reserved.

The occurrence of neritic microbial carbonates is often related to ecological refuges, where grazers and other competitors are reduced by environmental conditions, or to post-extinction events (e.g. in the Late Devonian, Early Triassic). Here, we present evidence for Middle Jurassic (Bajocian) microbial mounds formed in the normal marine, shallow neritic setting of an inner, ramp system from the High Atlas of Morocco. The microbial mounds are embedded in cross-bedded oolitic facies. Individual mounds show low relief domal geometries (up to 3 m high and 4.5 m across), but occasionally a second generation of mounds exhibits tabular geometries (

A critical revision of published data along with new field data allow to draw up the succession of the fish faunas from the Lower Cenomanian to the Lower Turonian in the Tafilalt basin and surrounding areas (southeast Morocco). The analysis of these faunas shows changes from freshwater to marine palaeoenvironments. The palaeogeographic distribution of some taxa is discussed. It shows that the crossing of strictly freshwater organisms between Africa and South America was likely impossible at the time of the formation of the deposits resting around the Tafilalt basin and named ‘Kem Kem beds’. The Cenomano-Turonian transgression reached the Erfoud–Errachidia carbonate platform from the Central Tethys, and then connected the central Atlantic.