Spatial and temporal facies evolution of a Lower Jurassic carbonate platform, NW Tethyan margin (Mallorca, Spain)

The variety of depositional facies of a Lower Jurassic carbonate platform has been investigated on the island of Mallorca along a transect comprising six stratigraphic profiles. Twenty-nine facies and sub-facies have been recognized, grouped into seven facies associations, ranging in depositional environment from supratidal/terrestrial and peritidal to outer platform. Spatial and temporal (2D) facies distribution along the transect reflects the evolution of the carbonate platform with time showing different facies associations, from a broad peritidal platform (stage 1) to a muddy open platform (stage 2), and finally to a peritidal to outer carbonate platform (stage 3). Stage 1 (early Sinemurian to earliest late Sinemurian) corresponds to a nearly-flat peritidal-shallow subtidal epicontinental platform with facies belts that shifted far and fast over the whole study area. The evolution from stage 1 to stage 2 (late Sinemurian) represents a rapid flooding of the epicontinental shallow platform, with more open-marine conditions, and the onset of differential subsidence. During stage 3 (latest Sinemurian), peritidal and shallow-platform environments preferentially developed to the northeast (Llevant Mountains domain) with a rapid transition to middle-outer platform environments toward the northwest (Tramuntana Range domain). Stages 1 and 3 present facies associations typical of Bahamian-type carbonates, whereas stage 2 represents the demise of the Bahamian-type carbonate factory and proliferation of muddy substrates with suspension-feeders. The described platform evolution responded to the interplay between the initial extensional tectonic phases related to Early Jurassic Tethyan rifting, contemporaneous environmental perturbations, and progressive platform flooding related to the Late Triassic–Early Jurassic worldwide marine transgression and associated accommodation changes

Les monticules micritiques sinemuriens sur la transversale de Midelt-Errachidia (Haut Atlas Central, Maroc)

In the central High Atlas of Morocco, the Liassic series present different mud-moundtype carbonate buildups, well developed in the Midelt area, towards the boundary between the Lower and the Upper Sinemurian. Near Foum Tillicht, these structures show a real evolution within the Upper Sinemunan interval, from simple small-scale bodies at the base, up to big and complex forms at the top. Their sedimentological and palaeontological features indicate microbolites and sponge buildings developed in deep and open marine conditions, within the subphotic zone, at the lower part of the storm wave interval. These buildups are closely linked to tectonic processes as they grow on the normal synsedimentary faults which affected the central atlasic area during the Lower Liassic period, leading to the breakup of the Early Sinemurian carbonate platform and the induced installation of the Upper Sinemurian subsiding basin. Silting by hemipelagic sediments led to death of buildings. Similar palaeogeographic changes and geodynamic evolution have been recently described from different structures in North Africa, Western Europe and North America.<br><br>Le L&iacute;as du Haut Atlas central marocain pr&eacute;sente diverses&quot;bioconstructions carbonat&eacute;es de type Mud-mound bien d&eacute;velopp&eacute;es au passage Sin&eacute;murien inf&eacute;rieur- Sin&eacute;murien sup&eacute;rieur au Sud de Midelt. Ces structures &eacute;voluent tr&egrave;s localement, a Foum Tillicht, dans tout l&rsquo;intervalle Sin&eacute;murien sup&eacute;rieur. Elles pr&eacute;sentent des formes et des tailles respectivement simples et r&eacute;duites a la base de la s&eacute;rie et deviennent complexes et de grande dimension au sommet. Leurs caract&eacute;ristiques s&eacute;dimentologiques et pal&eacute;ontologiques montrent qu&rsquo;il s&rsquo;agit de constructions a microbolites et a spongiaires d&eacute;velopp&eacute;es dans un milieu marin ouvert et profond, dans la zone subphotique, a la partie inf&eacute;rieure de la zone d&rsquo;action des vagues de temp&ecirc;te. L&rsquo;apparition et le grand d&eacute;veloppement des bioconstructions boueuses sin&eacute;muriennes sont associ&eacute;s a un changement de la morphologie du fond marin induit par la phase majeure de dislocation de la plateforme au passage Sin&eacute;murien inf&eacute;rieur-Sin&eacute;murien sup&eacute;rieur. L&rsquo;augmentation verticale de leur taille indiquerait un accroissement de la subsidence et du taux de s&eacute;dimentation carbonat&eacute;e, en relation avec l&rsquo;augmentation de l&rsquo;intensit&eacute; de la fracturation. La disparition de ces monticules, au passage Sin&eacute;murien-Carixien, est due a un envasement par des s&eacute;diments h&eacute;mip&eacute;lagiques de bassin cons&eacute;cutif h un approfondissement du milieu. Cet exemple haut atlasique se r&eacute;v&egrave;le ainsi comparable aux mod&egrave;les r&eacute;cemment propos&eacute;s pour expliquer le d&eacute;veloppement des mud-mounds connus en Afrique du Nord, en Europe occidentale et en Am&eacute;rique du Nord

The Liassic mud-mounds from Central High Atlas (Morocco). Stratigraphie and geodynamic settings

Chafiki D., Souhel Abdellatif, Canerot J., Ibouh H., El Hariri Khadijia, Taj-Eddine Kamal. The Liassic mud-mounds from Central High Atlas (Morocco). Stratigraphie and geodynamic settings. In: Géologie Méditerranéenne. Tome 28, numéro 1-2, 2001. Anatomy of Carbonate Bodies / Anatomie des corps carbonates. International Meeting / Colloque international. Marseille, 9-12 mai 2001, France, sous la direction de Marc Floquet, Jérôme Hennuy et Jean-Pierre Masse. pp. 49-52

SILICEOUS SPONGES AND MICROBIALITE CARBONATE MOUNDS AND THEIR ENVIRONMENT AT THE SINEMURIAN OF NZALA AND FOUM TILLICHT, CENTRAL HIGH ATLAS (MOROCCO)

The Nzala and Foum Tillicht outcrops that occur North of Rich village, are part of the Sinemurian carbonate mounds well exposed all over the Midelt-Errachidia transect in central High-Atlas (Morocco). These mounds constitute the upper part in the upper member of the Idikel formation, dated by ammonites, in the Lower-Upper Sinemurian transition. They locally grow in the Upper Sinemurian and disappear at the bottom of the Lower Carixian. The biosedimentological study of these carbonate mound, allowed the distinction between three different sets: a lower set (25 m) where the carbonate mounds are simple shaped and small sized boundstones, dominated by calcified sponges in a life position, including hexactinellides sponges, lithistids demosponges and non-rigid Demospongiae; a medium set (35 m) which shows complex shaped and big sized constructions including sponges and different thrombolytic fabric (clotted, digitate and dendrolitic). And an upper set, the most developed (150 m) consists of a vertical arrangement of lenticular structures of metric width and decametric extension where the thrombolites and sponges are very rare. This set shows some solitary corals and a hardened surface rich in ammonite of the base of lower carixian. The analysis of an elementary mound type show, essentially two parts: - A massif micritic-dominated core, which is a boundstone dominated by siliceous sponges and microbialites with associated encrusting forms (Radiomura, Serpula and Terebella, Tubiphytes and Bryozoans), beside, brachiopods, pelecypods, gastropods, isolated corals, ostracods, hyaline foraminifera and ammonites. - A well bedded sediments, corresponding to the core lateral synchronous, showing a biocalcarenitic facies a proximal to the core and a biomicritic facies further laterally. Brachiopods and echinoderms are particularly abundant. Complete or fragmented bivalve and gastropod shells are common. The studied outcrops resulted volumetrically dominated by siliceous sponges and microbialites that represent the major constructor and stabilizer, in addition to such benthic assemblage described previously, suggest an open marine depositional environment, infratidal to circatidal and relatively low energy

Bulk-carbonate and belemnite carbon-isotope records across the Pliensbachian-Toarcian boundary on the northern margin of Gondwana (Issouka, Middle Atlas, Morocco)

publisher: Elsevier articletitle: Bulk-carbonate and belemnite carbon-isotope records across the Pliensbachian-Toarcian boundary on the northern margin of Gondwana (Issouka, Middle Atlas, Morocco) journaltitle: Palaeogeography, Palaeoclimatology, Palaeoecology articlelink: http://dx.doi.org/10.1016/j.palaeo.2016.11.014 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved