Sadki Driss

Université Moulay Ismail | UMI · Geology

In the Moroccan Atlas, sedimentary deposits provide important data on reef events that characterize the Jurassic period. Recent work allows us to enhance knowledge of the Jurassic reefs in the Atlas, in particular their age, character and palaeogeographic distribution. Numerous localities with sponge-microbial mud mounds, coral reefs, and lithiotid bioherms are recorded from the Middle and High Atlas regions. These different biogenic constructions occupy different palaeogeographic settings: on the top of tilted blocks within the basin center; in slightly deeper positions, at the basin platform junction; and on adjacent platforms in the middle of the coastal area. The main episodes of reef building span nearly 30 million years, as follows: (1) Sinemurian, (2) early Pliensbachian, (3) late Toarcian, (4) Aalenian–early Bajocian (pars), and (5) late Bajocian. These five distinct reef events can be linked with general fluctuations of sea level and tectonism, and have palaeoclimatic implications.

The "niveau brun", dated as lower Toarcian outcrops in the northern Middle Atlas. It shows thickness and lateral facies variations. In the north-east Middle Atlas, the "niveau brun" which has turbiditic character, shows Bouma sequences generaly truncated in their bases. Four sub-facies of MUTTI & RICCI-LUCCHI (1975) are recognized, and a locally chaotic facies resulting from slides of unconsolidated sediments. The abundance of C and D sub-facies shows that the "niveau brun" comesponds to distal turbidites, which are interrupted by deposition of local material. These turbidites are deposited in the outer part of a deep-sea fan. These calciturbidites are contemporaneous of a tectonic regional episode wich causes the emersion of the "Causse moyen atlasique" and the south-west part of the Middle Atlas. The eroded detrital products fill then the northern subsident basin.

Serpulid-dominated shell beds from the Lower Bajocian (Middle Jurassic) of the Central High Atlas (Morocco) are primarily formed by quadrangular tubes of the serpulid polychaete Nogrobs moroccensis sp. nov. The transverse tube ornament consisting predominately of wrinkles, the lack of narrow spirals and the shortness or absence of attached posterior tube portion represent the diagnostic features of this new species. Tubes of Nogrobs moroccensis co-occur with gastropods and oyster–crinoidal debris. We suggest that these serpulids were free-lying in their adult stage and formed benthic meadows on soft-bottom habitats. They frequently show parallel alignment in plane views in both graded and non-graded, few-cm-thick shell beds, corresponding to distal tempestites deposited close to and below storm wave base in an outer-ramp environment. The excellent preservation of serpulids implies short residence time on the seafloor, and the lack of compositional mixing with other communities and their restriction to outer-ramp habitats indicate that they represent parautochthonous assemblages. Analyses of serpulid orientation on the bottom bedding planes of shell beds revealed weak unidirectional arrangement of tubes, whereas orientation on the top bedding planes revealed strong unidirectional arrangement of tubes, with significantly different orientation relative to the bottom planes. This change could suggest a shift from predominantly a current component of the combined storm flow (with uneven seafloor surface and adhesion of skeletal grains to muddy substrate) to significant oscillatory component of the waning storm, as also suggested by bidirectional orientation of gastropods.

Serpulid-dominated shell beds from the Lower Bajocian (Middle Jurassic) of the Central High Atlas (Morocco) are primarily formed by quadrangular tubes of the serpulid polychaete Nogrobs moroccensis sp. nov. The transverse tube ornament consisting predominately of wrinkles, the lack of narrow spirals and the shortness or absence of attached posterior tube portion represent the diagnostic features of this new species. Tubes of Nogrobs moroccensis co-occur with gastropods and oyster–crinoidal debris. We suggest that these serpulids were free-lying in their adult stage and formed benthic meadows on soft-bottom habitats. They frequently show parallel alignment in plane views in both graded and non-graded, few-cm-thick shell beds, corresponding to distal tempestites deposited close to and below storm wave base in an outer-ramp environment. The excellent preservation of serpulids implies short residence time on the seafloor, and the lack of compositional mixing with other communities and their restriction to outer-ramp habitats indicate that they represent parautochthonous assemblages. Analyses of serpulid orientation on the bottom bedding planes of shell beds revealed weak unidirectional arrangement of tubes, whereas orientation on the top bedding planes revealed strong unidirectional arrangement of tubes, with significantly different orientation relative to the bottom planes. This change could suggest a shift from predominantly a current component of the combined storm flow (with uneven seafloor surface and adhesion of skeletal grains to muddy substrate) to significant oscillatory component of the waning storm, as also suggested by bidirectional orientation of gastropods.

The early Middle Jurassic represents an interval of important taxonomic diversification in belemnites in the Western Tethys. Field work in the Moroccan Atlas mountains has permitted to collect numerous belemnite rostra, ranging from the uppermost Aalenian (Concavum Zone) to the lower Bajocian (Propinquans Zone). Seven species belonging to the genera Holcobelus, Calabribelus, Belemnopsis, Conobelemnopsis and?Dicoelites (all suborder Belemnopseina) are described for the first time from the Middle Atlas (area of Boulemane) and the Central High Atlas (area of Rich). The taxonomic composition of the genus Calabribelus is re-discussed in the light of the new findings, including the description of C. combemoreli sp. nov. The taxonomic analysis evidences strong affinities with Belemnopseina-dominated faunas from the French Subalpine Basin (SE France) and Calabria (South Italy). These Mediterranean assemblages strongly differ in taxonomic composition from coeval boreal belemnite faunas of NW Europe, characterized by a predominance of the suborder Belemnitina. The new records from Morocco confirm that during the late Aalenian and early Bajocian faunal segregation between Mediterranean (Tethyan domain) and Euro-Boreal (Boreal domain) assemblages is fully expressed, for the first time in the evolutionary history of belemnites. ©2017 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.

The early Middle Jurassic represents an interval of important taxonomic diversification in belemnites in the Western Tethys. Field work in the Moroccan Atlas mountains has permitted to collect numerous belemnite rostra, ranging from the uppermost Aalenian (Concavum Zone) to the lower Bajocian (Propinquans Zone). Seven species belonging to the generaHolcobelus, Calabribelus, Belemnopsis, Conobelemnopsis and ?Dicoelites (all suborder Belemnopseina) are described for the first time from the Middle Atlas (area of Boulemane) and the Central High Atlas (area of Rich). The taxonomic composition of the genus Calabribelus is re-discussed in the light of the new findings, including the description of C. combemoreli sp. nov. The taxonomic analysis evidences strong affinities with Belemnopseina-dominated faunas from the French Subalpine Basin (SE France) and Calabria (South Italy). These Mediterranean assemblages strongly differ in taxonomic composition from coeval boreal belemnite faunas of NW Europe, characterized by a predominance of the suborder Belemnitina. The new records from Morocco confirm that during the late Aalenian and early Bajocian faunal segregation between Mediterranean (Tethyan domain) and Euro-Boreal (Boreal domain) assemblages is fully expressed, for the first time in the evolutionary history of belemnites.

Earth is a material widely available in our immediate environment. It's the basic raw material used in the vernacular housing in Morocco, the pre-Saharan regions, and in the majority of historic centers. The plain soil's of the Haouz of Marrakesh is renowned for its abundance in materials suitable to construction of earth habitats. The use of earth material in construction in Morocco has become topical, as, the strong demand for low-cost housing. The fundamental reason of this demand is probably the very high cost of conventional building materials. For the Moroccan government, the construction of earth habitat is an economical alternative which respects the environment. The recent approval of the seismic resolution for the earth construction (RPCT2011) by the Moroccan Government is an action for the recovery of this natural resource and maintenance of traditional knowledge attached to earth architecture. This is a historic step forward for the promotion of sustainable habitat. The valuation of this natural resource is dependent on the identification of suitable borrow sites, the study of its physical and chemical properties and its mechanical characteristics and appropriate construction techniques. It is in this perspective that our laboratory is active in the operational research on sites around the city of Marrakesh, potentially rich earthen resources, tailored to the promotion of the construction.

The field work carried on by the Paleontological section of the National Museum for Natural History (Luxembourg) and collaborators in the ‘Couches à Sonninia’ (Bajocian, Middle Jurassic) of southern Luxembourg, during 1984 and 2010, yielded numerous well preserved ammonites. The specimens are referred to the genera Hyperlioceras, Euhoploceras, Fissilobiceras, Nannoceras, Pseuodshirbuirnia, Shirbuirnia, Emileia and are herein described for the first time from Luxembourg. As a complement to ammonites, new specimens of belemnites referred to the genera Eocylindroteuthis and Brevibelus are reported herein, with comments on their stratigraphic position. The palaeontological analysis of the ammonite assemblage provides further biostratigraphic details for the lithological units of the lower Bajocian in Luxembourg.

This work presents an integrated biostratigraphic study across the Aalenian/Bajocian boundary of the Central High Atlas of Morocco. The data that are the basis for this study were obtained from the region of Rich that is located in the center of the basin of the Moroccan High Atlas. This region presents a thick Aalenian–Bajocian succession with continuous marine sedimentation, which offers a rich and varied fauna whose analysis enables the compilation of an integrated biostratigraphy based on the different paleontological groups:

La biogéographie des ammonites de l’Aalénien supérieur-Bajocien inférieur est abordée de façon quantitative. Ainsi, le calcul d’indices de similarité et de distance fauniques (méthode multivariée) a permis de comparer neuf régions appartenant à des provinces paléobiogéographiques différentes. La comparaison de ces régions entre elles, tous intervalles con-fondus, fait apparaître l’existence d’une parfaite relation entre la position géographique des régions, la physiographie des bassins et la composition taxonomique. En revanche, la compa-raison pour chaque intervalle chronologique montre au contraire, la grande stabilité dans le temps des faunes dans quatre régions (Cordillère Bétique, Cordillère Ibérique, Haut-Atlas central et Bassin Lusitanien), la fluctuation des faunes dans trois régions (Dorset-Somerset, Bassin du Sud-Est de la France et Moyen-Atlas plissé) et enfin l’isolement des faunes dans deux régions (Béni Snassen et Appennins d’Ombrie-Marches).

The Lower Jurassic characterisation and particularly the Pliensbachian–Toarcian limit is of a paramount importance in the geological history of the Atlantic and the circum-Mediterranean field. In the Moroccan central High Atlas and in the Todrha-Dades region particularly, this passage is similar to a hinge area marked with tectono-eustatic and bio-sedimentary events.RésuméLa caractérisation de la limite Pliensbachien–Toarcien revêt une grande importance dans l’histoire géologique du domaine atlasique et du domaine circum-méditerranéen. Dans le Haut Atlas central marocain, en particulier dans la région de Todrha-Dadès, ce passage correspond à une époque charnière, marquée par des événements bio-sédimentaires et tectono-eustatiques.

The Lower Jurassic characterisation and particularly the Pliensbachian-Toarcian limit is of a paramount importance in the geological history of the Atlantic and the circum-Mediterranean field. In the Moroccan central High Atlas and in the Todrha-Dades region particularly, this passage is similar to a hinge area marked with tectono-eustatic and bio-sedimentary events. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS.

In the central High Atlas Montains, the passage Pliensbachian-Toarcian is not always well recorded. It is marked in the pliensbachian platform by shortag in the form of eroded hiatus (Atlas of Azilal, western zone of the central High Atlas, region of Todrha-Dadès: HARTD). Geological sections realised in the HARTD, have delivered the ammonites that precisely marked the passage Pliensbachian-Toarcian in a space and a temporal context. This passage has been observed between the Ouchbis formation and Tagoudite's one. It has also made the object of an faciologic and sedimentologic analysis. The discontinuity "post-pliensbachienne" which is marked approximately in the central High Atlas corresponds to an important rupture sedimentary in connection with a crisis tectono-eustatic causing the dislocation of the carbonate platform. In the HARTD this event is underlined also by an angular disconformity observed in the location of Ikerzi. It limits two formations: Aberdouz in the basis and Bin El Ouidane in the summit dated by the brachiopoda and foraminifera. The ammonites gathered at the level of this passage present a mesogean seal. The early Toarcian ammonites disappears just before a large level oxidized bioturbations that in our sector that we have considered as an inferior limit by the formation of Tagoudite. This ammonites extinction is synchronic to a radical change of the sedimentary facies marked by the passage of the Pliensbachian with turbidites limestones to the turbidites silicoclastics of the lower Toarcian by the formation of Tagoudite. Associations of ammonites have allowed us to establish correlations with Northern and Western zone of the High Atlas, and the Mediterranean area.

A sequential analysis of Liasic deposits in the northern margins of the High Atlas range at Béni-Mellal led to the identification of eight sequences of the third order for the Upper Sinemurian-Lower Toarcien interval. The age as well as the sedimentary characteristics of the deposits are described in this study

The Rich area, situated in the center of the basin of High Moroccan Atlas, presents a thick Aalenian - Bajocian succession with continuous marine sedimentation, which offers a rich and varied fauna. The boundary between the two stages is marked by the first appearance of Hyperlioceras together with numerous mediterranean elements, which also enables good corrlations. Therefore, thanks to its easy access, its thick continuous and well exposed deposits, and the richness and variety of its fauna, we propose this area as a submediterranean auxiliary stratotype for the boundary between Aalenian and Bajocian.

ABSTOACT [BRACHIOPOD BIOSTRATIGRAPHY OF THE MlDDLE JURASSIC OF THE ATLASIC DOMAIN (MOROCCO, ALGERIA). ENVIRONNMENTAL STRESSES AND COMPARISON WITH THE VERTICAL EVOLUTION OF THE AMMONITES COMMUNITIES]: The recent papers on Brachiopods (SADKJ & ALMÉRAS, 1992 ; ALMÉRAS & SADKI, 1992) collected in the Central High-Atlas, neighbourhood of Rich and South of Midelt (Morocco), the unpublished detailed sections studied in the Ksour Mountains (Saharan Atlas of Algeria), the unpublished paleontological revision of Brachiopods collected during these last ten years in many localities with ammonite faunas, allow us to propose now a biostratigraphical succession of Middle Jurassic Brachiopods suitable to the Atlasic Domain. This Brachiopod scale is correlated with that established in the French Tethyan Domain. In the Ksour Mountains, it confirms the great thickness of sediments deposited during the Niortense Zone ; it also evidences the reduced thickness of beds corresponding to Upper Bajocian and Lowermost Bathonian (Garantiana pars Zone until the Convergens Subzone of the Zigzag Zone). The main other results are paleoecological and paleobiogeographical. The paleoecological data concern Flabellothyris oranensis, a perireefal and epireefal brachiopod which sets up and develops when the reefal phases stop, after the flooding of bioconstructions and the too fast substrate sinking. A paleobiogeographical ségrégation has been observed between uniplicate or sulciplicate Cereritbyris located to the borders of the atlasic furrow (where they belong to plurispecific communities) and the Holcothyris with their inverted type of folding, probably better adapted to the subsiding furrow axis conditions {monospecific communities). Ail these Brachiopods are abundant at the top of filling up sequences, at the exception of Flabellothyris oranensis which appears after slight rises of the relative sea-Ievel, perturbating the overall régressive trend. Arabie faunas (Ermoceras) penetrate the Adasic Domain during the Niortense Zone as the previous subsiding furrows are filled by prograding neritic deposits. The différences between the communities of the Atlasic Domain ("ethiopian" affinity) and the Tlemcenian Domain ("alpine" affinitv) are stressed and situated within the biogeographical distribution scheme of the Tethys. The relative physiographical position in the studied areas is also a main control of the distribution of the brachiopods and, often, of the ammonites.

Three condensed beds overlying discontinuities interpreted as flooding surfaces (s.l.) have been located in a Late Toarcian-Early Bajocian section of the Central High Atlas (Morocco). Taking into account the shell morphologies, the faunal compositions are quite similar in the condensed beds where evolute shells abound. On the contrary, the mainly calcareous deposits intercalated between the condensed beds yield mainly involute shells (especially suboxycone). So, the episodes of fast increases in relative sea levels seem to have considerably affected the ammonite associations. There is an abridged English version. -English summary

The discontinuities are analysed and precisely correlated with the biostratigraphical scale. The Lotharingian discontinuity marks a first stage of the subsidence when the form of the basin was established. At the Pliensbachian-Toarcian boundary an important sedimentary break resulted from the progressive fragmentation of the Liassic platform. The general tectonic framework of the basin then included the classic elements of margins, grabens and horst. After these major sedimentary breaks, there followed a number of local (ante-Gradata, ante-Insigne, post-Bradfordensis) or regional (post-Opalinum, post-Concavum, post-Laeviuscula) discontinuities. It is debatable whether the discontinuities are caused by tectonic events, eustatic sea-level events or perhaps to a combination of the two as a result of interrelationship within the framework of the geodynamic evolution of the Tethys and Atlantic. -from English summary

In the Kasbat Flilo section Lower Bajocian marls and alternating marls and limestones are exposed, topped by the "Calcaire corniche' (probably Upper Bajocian). Several levels dated by ammonites have yielded the numerous brachiopods studied in this paper. Biostratigraphic results and evidence of miniaturization are discussed. The miniaturization represents a selective adaptative strategy to drastic environmental conditions unfavourable for benthic life and the optimal growth of shells. Palaeobiogeographical data indicate Arabian and Middle-East affinities of the main components of the brachiopod fauna. -from English summary

Three cycles, which are determined by tectonic and eustatic events are defined. The first cycle goes on until the Pliensbachian and corresponds to the onset of carbonate deposition in a proximal platform. The second cycle, first related to a tectonic activity which is paroxysmic in Domerian-Toarcian, is afterwards marked by reduced or lacunar deposits during Upper Toarcian-Lower Bajocian. Finally, the third cycle shows a return to stability and corresponds to a maximum eustatic rising. It is revealed by a thick marly layer in the Lower Bajocian, (Sauzei zone) recovering both the basin and its border. -from English summary

Aalenian-Bajocian limit beds of Cape Mondego have been the subject of recent revision. Lower Bajocian ancient and recent material had provided the recognition of four zones and a few subzones. Aalenian-Bajocian limit beds are relatively rich in Graphoceratids. In order to establish Concavum-Discites biozones limit we have used the presence of the most ancient representatives among the Hyperlioceras-Toxolioceras group. Euhoploceras, Sonninia, Fontannesia, Zurcheria and Parazurcheria representatives are still abundant at Discites Biozone. The relative frequency of Emileites, Witchellia and Fissilobiceras allows the subdivision of Laeviuscula Biozone into two distinguishable subzones. Basal Ovalis Subzone has been characterised by Witchellia's oldest representative; otoitids such as "Docidoceras" gr. longalvum, Emileites and Trilobiticeras s.l. may be locally predominant. Laeviuscula Subzone has been characterised by the first occurrence of W. Laeviuscula index species representatives. Haploceratids such as Bradfordia, Protoecotraustes, Toxamblyites, Microtoxamblyites and Lissoceras are frequent. Sauzei Biozone has been characterised by Labyrinthoceras apparition and Frogdenites absence. Haploceratids are quite common in most of the beds. Sonninids are very well represented at upper Sauzei Biozone. Stephanoceras nodosum is the first characteristic species found at Humphriesianum Biozone; Emileites and Otoites are absent but Dorsetensia and Nannoceras are still present.

The Upper Liassic-Bajocian Foraminifera and Ostracoda of the Talghemt area (central High Atlas, Morocco). The study of the stratigraphic distribution of the Toarcian to Bajocian microfauna (Foraminifera and Ostracoda) in the Talghemt area (central High Atlas, Morocco) allowed to recognize five micropaleontological assemblages. A large part of the Foraminifera and Ostracoda groups extends into the Early Toarcian. Among the Foraminifera, three important renewals occured : the first one at the top of the Polymorphum Zone, the second at the Bifrons-Gradata zones boundary, and the third in the Humphriesianum Zone. Among the Ostracoda, the renewals occured in the Polymorphum, the Bifrons and the Speciosum zones of the Toarcian and in the Humphriesianum Zone of the Early Bajocian The Foraminifera and Ostracoda distribution in the Toarcian is different from that of other basins. This is due to the particular physiography of the Talghemt area with an isolated through ("ombilic") where anoxic conditions and turbiditic influx are inhospitable for benthic life. In the Bajocian, food availability and more oxygenated outer shelf environment enabled a notable increase in the microfauna.

The late Toarcian and early Bajocian deposits of the south-eastern part of the Middle Atlas are diversified. These deposits show lateral variations of facies and thickness. Five depositional sequences are identified. The first three sequences, very developed in the subsiding area, are reduced and locally show gaps at the margin. They reflect a SW-NE palaeogeographic differentiation, controlled by transverse faults. The two upper sequences show homogeneous deposits of deep environment. These sequences controlled by eustatism and tectonics, become integrated into two second order regressive and transgressive half- cycles.

Located between the High Moulouya plain and the central High Atlas mountain, the evolution of Midelt during the Jurassic is largely conditioned by the dislocation of the liasic platform., The paroxysm of this event is responsible for the structuration of the area in tilted blocks, organised in mosaic of small basins separated by shallows showing tree panoramas : 1) the High-Moulouya plain is the seat of gaps and reduction in thickness,. 2) the zone of the passage of the northern High Atlas accident constitutes an paleorelief without any sedimentation, 3) Jebel Ayyachi (High Atlas) as a subsiding basin. Thus, the Jurassique sedimentation is controlled by local (tectonic) and global (eustatism) factors.