La limite Cénomanien-Turonien dans le Haut Atlas central, Maroc

Sur la bordure nord du Haut Atlas central, de nouvelles observations lithologiques et biostratigraphiques effectuées en particulier dans le synclinal de Naour, permettent de cerner avec précision la limite Cénomanien-Turonien. La reconnaissance dans cette structure d'une succession apparemment complète de l'intervalle Cénomanien supérieur-Turonien, la série de Ben Cherrou, nous incite à la proposer comme coupe de référence d'une Formation Ben Cherrou venant en remplacement de celle incomplète et donc moins représentative d'Aït Attab. Enfin, les caractéristiques sédimentologiques et paléontologiques des séries analysées suggèrent une origine téthysienne des transgressions cénomano-turoniennes de cette partie du domaine atlasique marocain.On the northern side of the Central High Atlas, new lithological and biostratigraphical data, especially realized in the Naour syncline, allow us to precise the Cenomanian-Turonian boundary. We recognized in that syncline an apparently complete series, the Ben Cherrou series, that represent the Upper Cenomanian-Turonian interval. We recommend it as the referring section of the Ben Cherrou Formation, that takes the place of the incomplete and not representative Aït Attab Formation. More, the sedimentological and paleontological analysis, suggest a Tethyan origin for the Cenomanian-Turonian transgressions in the studied area

Essai de caractérisation bio et lithostratigraphique des séquences sédimentaires dans le Crétacé moyen de la région d'Imi N'Tanout (Haut Atlas occidental, Maroc)

An attempt at a bio and lithostratigraphical characterization of sedimentary sequences in the Mid-Cretaceous of Imi N'Tanout area (Western High Atlas, Morocco) The mid-Cretaceous deposits of Imi N'Tanout area (Western High Atlas) belong to the northern edge of the Agadir-Essaouira basin. They display restricted shelf margin environments during the Vraconian - Cenomanian ages, and open marine influences in the Turonian. These deposits are generally divided into three formations wich respectively, from bottom to top, are : -the Kechoula dolomitic Carbonates formation linked to Vraconian ; -the Aït Lamine Marls formation attributed to Cenomanian ; -the Casbah Agadir Carbonates formation, Turonian in age. A review of them, as well as the stratigraphical or sedimentological point of view, has been carried out and has permitted us : -to discover a few micropaleontological markers showing the proposed ages ; -to carry out classic and detailed sequence analysis ; -to recognize the existence of major discontinuities of regional extension at least. These new elements permit us to suggest a first attempt at interpretation in terms of the stratigraphie sequence. It seems possible to divide the considered period into seven depositional sequences. The first (SD1) would be mixed-up with the Vraconian Kechoula formation ; the other six (SD2 to SD7) are in the Cenomano-Turonian. If, in spite of stratigraphical imprécisions, these seven sequences are connected by number with the third order cycles of the UZA-2 supercycle of HAQ and cd. chart (1987), the interpretation of the system tracts, especially during the Vraconian -Cenomanian, remain particulary difficult.Le Crétacé moyen (Albien supérieur à Turonien) de la région d'imi N'Tanout est classiquement subdivisé en trois formations. Leur analyse tant strati graphique que sédimentologique permet de proposer un premier essai d'interprétation en terme de stratigraphie séquentielle. Il paraît possible de reconnaître dans l'intervalle de temps considéré. sept séquences de dépôt. La première (SD1) se confondrait avec la formation vraconienne du Kechoula ; les six autres (SD2 à SD7) s'étagent dans le Cénomano-Turonien. Si, aux imprécisions stratigraphiques près, ces sept séquences sont corrélables en nombre aux cycles de 3ème ordre du supercycle UZA-2 du diagramme de HAQ et al., (1987), l'interprétation des cortèges sédimentaires, surtout dans l'intervalle Vraconien-Cénomanien reste particulièrement délicate.Ettachfini El Mostafa, El Kamali Nezha, Bilotte Michel. Essai de caractérisation bio et lithostratigraphique des séquences sédimentaires dans le Crétacé moyen de la région d'Imi N'Tanout (Haut Atlas occidental, Maroc). In: Colloque franco-marocain de Géologie, Strasbourg, 24-26 mai 1989. Vol. II : Cycle alpin (fin). Quaternaire. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1989. pp. 71-81. (Sciences Géologiques. Mémoire, 84

Essai de caractérisation bio et lithostratigraphique des séquences sédimentaires dans le Crétacé moyen de la région d'Imi N'Tanout (Haut Atlas occidental, Maroc)

An attempt at a bio and lithostratigraphical characterization of sedimentary sequences in the Mid-Cretaceous of Imi N'Tanout area (Western High Atlas, Morocco) The mid-Cretaceous deposits of Imi N'Tanout area (Western High Atlas) belong to the northern edge of the Agadir-Essaouira basin. They display restricted shelf margin environments during the Vraconian - Cenomanian ages, and open marine influences in the Turonian. These deposits are generally divided into three formations wich respectively, from bottom to top, are : -the Kechoula dolomitic Carbonates formation linked to Vraconian ; -the Aït Lamine Marls formation attributed to Cenomanian ; -the Casbah Agadir Carbonates formation, Turonian in age. A review of them, as well as the stratigraphical or sedimentological point of view, has been carried out and has permitted us : -to discover a few micropaleontological markers showing the proposed ages ; -to carry out classic and detailed sequence analysis ; -to recognize the existence of major discontinuities of regional extension at least. These new elements permit us to suggest a first attempt at interpretation in terms of the stratigraphie sequence. It seems possible to divide the considered period into seven depositional sequences. The first (SD1) would be mixed-up with the Vraconian Kechoula formation ; the other six (SD2 to SD7) are in the Cenomano-Turonian. If, in spite of stratigraphical imprécisions, these seven sequences are connected by number with the third order cycles of the UZA-2 supercycle of HAQ and cd. chart (1987), the interpretation of the system tracts, especially during the Vraconian -Cenomanian, remain particulary difficult.Le Crétacé moyen (Albien supérieur à Turonien) de la région d'imi N'Tanout est classiquement subdivisé en trois formations. Leur analyse tant strati graphique que sédimentologique permet de proposer un premier essai d'interprétation en terme de stratigraphie séquentielle. Il paraît possible de reconnaître dans l'intervalle de temps considéré. sept séquences de dépôt. La première (SD1) se confondrait avec la formation vraconienne du Kechoula ; les six autres (SD2 à SD7) s'étagent dans le Cénomano-Turonien. Si, aux imprécisions stratigraphiques près, ces sept séquences sont corrélables en nombre aux cycles de 3ème ordre du supercycle UZA-2 du diagramme de HAQ et al., (1987), l'interprétation des cortèges sédimentaires, surtout dans l'intervalle Vraconien-Cénomanien reste particulièrement délicate.Ettachfini El Mostafa, El Kamali Nezha, Bilotte Michel. Essai de caractérisation bio et lithostratigraphique des séquences sédimentaires dans le Crétacé moyen de la région d'Imi N'Tanout (Haut Atlas occidental, Maroc). In: Colloque franco-marocain de Géologie, Strasbourg, 24-26 mai 1989. Vol. II : Cycle alpin (fin). Quaternaire. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1989. pp. 71-81. (Sciences Géologiques. Mémoire, 84

Le Berriasien et le Valanginien de l'Atlas Atlantique - Maroc. Biostratigraphie et séquences de dépôt

The Berriasian and Valanginian series of the Western High Atlas (Morocco) - Biostratigraphy and depositional sequences. The cretaceous series of the Atlantic High Atlas begins with two units which are accurately dated by their Ammonites and Calpionellids : the Agroud Ouadar Formation (Berriasian-basal Valanginian) and the Sidi Lhousseine Formation (Valanginian). Eight third order depositional sequences are identified, four during the Berriasian and four during the Valanginian. They are keeping in with a second order cycle, transgressive then regressive, ponctuated by two phases of distensive movements influencing the basin topography, the first one on the Tithonic-Berriasian boundary and the second one at the earlier Valanginian.Le Crétacé du Haut Atlas Atlantique débute par deux unités qui sont datées avec précision par leur faune d'Ammonites et Calpionelles : La Formation d'Agroud Ouadar, (Berriasien - Valanginien basal) et la Formation de Sidi Lhousseine (Valanginien). Huit séquences de dépôt de 3ème ordre ont été identifiées, quatre au Berriasien et quatre au Valanginien. Elles s'inscrivent dans un cycle de 2ème ordre transgressif puis régressif, ponctué par deux phases de tectonique distensive qui modifient brusquement la paléotopographie du bassin, la première à la limite Tithonique-Berriasien, la seconde au Valanginien basal.Taj-Eddine Kamal, Ettachfini El Mostafa, Rey Jacques. Le Berriasien et le Valanginien de l'Atlas Atlantique - Maroc. Biostratigraphie et séquences de dépôt. In: Géologie Méditerranéenne. Tome 19, numéro 1, 1992. pp. 41-50

Geospatial Assessment of Soil Organic Matter Variability at Sidi Bennour District in Doukkala Plain in Morocco

Understanding the spatial variability of soil organic matter (SOM) is critical for studying and assessing soil fertility and quality. This knowledge is important for soil management, which results in high crop yields at a reduced cost of crop production and helps to protect the environment. The benefits of an accurate interpolation of SOM spatial distribution are well known at the agricultural, economic, and ecological levels. It has been conducted this study for comparing and analyze different spatial interpolation methods to evaluate the spatial distribution of SOM in Sidi Bennour District, which is a semi-arid area in the irrigated scheme of the Doukkala Plain, Morocco. For conding this study, it was collected 368 representative soil samples at a depth of 0–30 cm. A portable global positioning system was used to obtain the location coordinates of soil sampling sites. The SOM spatial distribution was performed using four interpolation methods: inverse distance weighted and local polynomial interpolation as deterministic methods, and ordinary kriging and empirical Bayesian kriging as geostatistical methods. High SOM levels were concentrated in vertisols, and low SOM levels were observed in immature soils. The average SOM value was 1.346%, with moderate to high variability (CV = 35.720%). A low SOM concentration indicates a continuous possibility of soil degradation in the future. Ordinary kriging yielded better results than the other interpolation methods (RMSE = 0.395) with a semivariogram fitted by an exponential model, followed by inverse distance weighted (RMSE = 0.397), empirical Bayesian kriging (RMSE = 0.400), and local polynomial interpolation (RMSE = 0.412). Soil genetics and the strong influence of human activity are the major sources of SOM spatial dependence, which is moderate to low. Low SOM content levels (< 1.15%) were present in the southwestern and eastern parts of the digital map. This situation calls for the implementation of specific soil recovery measures

A Barremian-?Aptian Tethyan precursor of the Cretaceous marine flooding of Morocco: Evidence from the red-bed series within the “Marginal Folds” of the eastern High Atlas

International audienceStratigraphic, sedimentologic, and micropaleontologic studies have been undertaken on the “Infra-Cenomanian” continental red beds (= Dekkar Group) located on the northern side of the Moroccan eastern High Atlas. Rich charophyte assemblages containing Sphaerochara magna, Ascidiella stellata, Hemiclavator sp. A, Globator trochiliscoides, Atopochara trivolvis, At. triquetra, and Flabellochara harrisii indicate a late Barremian age for the lower part of the series. Within the continental deposits we have discovered in the Middle Member of the Dekkar 2 Formation limestones and marls containing echinoderms, dasycladacean algae and foraminifera (miliolids, Ammobaculites sp., Choffatella decipiens). The existence of two littoral to lagoonal-marine intercalations within the continental sedimentation reveals marine transgressive events during the late Barremian–?early Aptian. The lateral extension of these marine sediments allows the erection of paleogeographic boundaries that define a « Marginal Folds Gulf » characterized mainly by restricted marine paleoenvironments. This E-W directed gulf is a relatively long depression, a few tens of kilometers wide and one hundred kilometers long, developed in an area which is now at the foot of the eastern High Atlas. The infilling deposits is dominantly controlled by the distance from the North High Atlas Fault. The gulf terminated westward and probably opened northeastward into the Tethyan domain. This narrow gulf was separated from both the Tethyan Gulf known in the Central Middle Atlas during the Aptian and the coeval Atlantic Gulf located on the northern side of the Marrakech and Central High Atlas. Thus, the « Marginal Folds Gulf » is a new paleogeographic feature that documents marine incursions within the Jurassic–Early Cretaceous continental areas of the NW Africa