Papers by Nadia Mhammdi
Bulletin de l'Institut …, 2005
L'étude granulométrique des sables titanifères de l'estuaire de l'Oum Er-Rbia et du littoral d'Az... more L'étude granulométrique des sables titanifères de l'estuaire de l'Oum Er-Rbia et du littoral d'Azemmour a permis de caractériser la dynamique sédimentaire de cette zone. La morphoscopie des quartz a révélé la prédominance des émoussés luisants , traduisant l'importance du remaniement marin. L'analyse minéralogique de la fraction lourde montre l'abondance de l'ilménite et de la magnétite sur le reste des minéraux. Ils se concentrent sur les plages au voisinage de l'embouchure de l'Oued l'Oum Er-Rbia. La répartition de l'ilménite montre une évolution croissante du rivage vers la plage aérienne. Les marées, les courants , les vagues et le vent sont les agents responsable de la concentration de ces minéraux. Mots clés : Maroc, côte atlantique, sédimentologie, minéraux lourds, sables titanifères.
Résumé. Cette étude est basée sur la cartographie détaillée de la partie proximale de la platefor... more Résumé. Cette étude est basée sur la cartographie détaillée de la partie proximale de la plateforme atlantique marocaine au sud de Cap Spartel, menée à l'aide d'un sonar à balayage latéral (SBL) et complétée par des données sédimentologiques provenant de sources bibliographiques. Les images sonar SBL montrent une mosaïque complexe de substrats rocheux et de corps sédimentaires transversaux et longitudinaux aux courants dominants. L'analyse morphologique suggère que les courants de marée sont l'agent hydrodynamique principal qui contrôle le développement des petites structures. Mots clés : sonar à balayage latéral, plateau continental marocain, le large de Cap Spartel, dunes. Morphological study by side-scan sonar of the unconsolidated sediments of the Atlantic internal platform south of Tangier (Morocco). Abstract. This study is based on a detailed mapping of a sector of the proximal part of the Atlantic continental shelf located to the south of Cap Spartel (Morocco)...
Second International Conference on Engineering Geophysics, 2013
ABSTRACT The images of the water-sediment surface provided by the AUV, showing dunes in different... more ABSTRACT The images of the water-sediment surface provided by the AUV, showing dunes in different area of the loukkos river with a wavelength differs from 1 to 15 m; they are organized in series with quite the same lengths and the same wave amplitude. Another distinguishing criterion, revealed thanks to images of the water-sediment surface, seems to be the longitudinal morphology of dunes (planimetric dune morphologies). We were able to distinguish dunes with crests straight and slightly curvy form characterizing the two-dimensional dunes. Other forms of crests were distinguished, presenting the three-dimensional dunes are dunes with crest highly sinuous, catenary, linguoid, and lunate. The latter are often detected upstream or near the banks, remaining fairly stationary during the period of our study. The AUV images constitute the first step towards the understanding the distribution of different forms of dunes, in the Oued Loukkos estuary, thus well unveil the relationship between the sinuosity of dunes and hydrodynamic and sedimentary environmental conditions.
Analysis of the CARLA-11 core drilled along the lower Loukkos valley near Larache in northern Mor... more Analysis of the CARLA-11 core drilled along the lower Loukkos valley near Larache in northern Morocco shows a thin level of shelly sand at 465 to 482 cm depth, whose sedimentological features are those of a high-energy, certainly a tsunami deposit. The level can be subdivided into 3 subunits: Subunit 1 (6 cm) shows a sharp erosive base and comprises basal medium to coarse sands containing numerous marine shell fragments of bivalves, plant fragments and rip-up clasts of organic matter. Subunit 2 (7 cm) is a flame structure consisting of coarse sand containing a layer of organic matter and another one of greyish clay. Subunit 3 (4 cm) is similar to subunit 1 and consists of coarse sands containing numerous complete or broken shells of bivalves, plant fragments and dark organic matter. The deposit is mostly composed of subangular to subrounded quartz grains derived from nearby Miocene sandstones. Benthic and planctonic foraminifera are common within the samples. Magnetic susceptibility measurements show two major lows at ~350 cm, and especially at 477 cm within the high-energy deposit. Subunit 1 can be interpreted as the result of the first wave uprush of a tsunami,
MHAMMDI, N., SNOUSSI, M. MEDINA, & JAAIDI E. B., 2014. Recent sedimentation in the Northwest African shelf. In, Chivas, A.R & Chiocci, F.L..(Eds). Continental shelves during the last glacio eustatic cycle: Continental shelves of the world. The Geological Society, London, Memoir Geological Society London Memoirs
The review of the data gathered during the last five decades on the Northwest African continental... more The review of the data gathered during the last five decades on the Northwest African continental shelf within numerous research programmes shows that the sedimentary processes along the shelf are driven by long-term factors such as Quaternary glacial-interglacial periods and shelf morphology, and by short-term factors such as fluvial and eolian sediment supply, local climate (temperature, rainfall and wind) and hydrodynamic conditions (tides, swell, longshore current, the Canary Current and upwelling). Based on the sedimentary characteristics, the margin has been subdivided into four segments: northern Morocco (30°N-36°N) and the Grande Côte of Senegal (15°N-16°30’N) show long mid-shelf mud belts controlled by fluvial input and low hydrodynamic energy; southern Morocco-Mauritania (16°30’N-30°N) and the Petite Côte south of Cap Vert, Gambia and Casamance (12°N-15°N) are dominated by biogenic and eolian sands or no sediment input. In this chapter, we present a synopsis of the state o...
Résumé. Cette étude est basée sur la cartographie détaillée de la partie proximale de la platefor... more Résumé. Cette étude est basée sur la cartographie détaillée de la partie proximale de la plateforme atlantique marocaine au sud de Cap Spartel, menée à l'aide d'un sonar à balayage latéral (SBL) et complétée par des données sédimentologiques provenant de sources bibliographiques. Les images sonar SBL montrent une mosaïque complexe de substrats rocheux et de corps sédimentaires transversaux et longitudinaux aux courants dominants. L'analyse morphologique suggère que les courants de marée sont l'agent hydrodynamique principal qui contrôle le développement des petites structures. Mots clés : sonar à balayage latéral, plateau continental marocain, le large de Cap Spartel, dunes. Morphological study by side-scan sonar of the unconsolidated sediments of the Atlantic internal platform south of Tangier (Morocco). Abstract. This study is based on a detailed mapping of a sector of the proximal part of the Atlantic continental shelf located to the south of Cap Spartel (Morocco)...
Second International Conference on Engineering Geophysics, 2013
ABSTRACT The images of the water-sediment surface provided by the AUV, showing dunes in different... more ABSTRACT The images of the water-sediment surface provided by the AUV, showing dunes in different area of the loukkos river with a wavelength differs from 1 to 15 m; they are organized in series with quite the same lengths and the same wave amplitude. Another distinguishing criterion, revealed thanks to images of the water-sediment surface, seems to be the longitudinal morphology of dunes (planimetric dune morphologies). We were able to distinguish dunes with crests straight and slightly curvy form characterizing the two-dimensional dunes. Other forms of crests were distinguished, presenting the three-dimensional dunes are dunes with crest highly sinuous, catenary, linguoid, and lunate. The latter are often detected upstream or near the banks, remaining fairly stationary during the period of our study. The AUV images constitute the first step towards the understanding the distribution of different forms of dunes, in the Oued Loukkos estuary, thus well unveil the relationship between the sinuosity of dunes and hydrodynamic and sedimentary environmental conditions.
SpringerPlus, 2015
In order to assess the changes in sea-surface hydrology and productivity signal from the last gla... more In order to assess the changes in sea-surface hydrology and productivity signal from the last glacial to the Holocene; a set of isotopic, geochemical and microgranulometric proxies was used for this study. Former studies revealed that the reconstruction of paleoproductivity from ocean sediment gives different results depending the measurement used. The comparison between our productivity proxies (total organic carbon, carbonate and planktonic δ 13 C) as well as previous results in nearby location indicates that the planktonic δ 13 C responds better to marine productivity changes and represents therefore a suitable proxy for paleoproductivity reconstruction in our studied area. The productivity signal reveals two main enrichments during the Young Dryas (YD) and the Heinrich Event 1 (HE 1) and correlates perfectly with upwelling activity mentioned by an increasing trend of aeolian proxies. In addition, our results show that biogenic components in the sediment have a marine origin and the proportion of organic matter preserved depends on the total sediment accumulation rate.
Natural Hazards, 2011
The coastal areas of south-west Iberia and north-west Morocco host numerous megaclast accumulatio... more The coastal areas of south-west Iberia and north-west Morocco host numerous megaclast accumulations thought to have been emplaced by high-energy waves, namely by the major tsunami related to the 1 November 1755 AD earthquake. New observations were carried out along several transects from Rabat and Larache areas, using statistical methods applied to boulder size. The main results are (a) the boulders belong to two or three sources located within the Pleistocene-Holocene formations of both areas, but only from a single source at Harhoura; (b) the boulders in Larache are generally small, thin and show a normal polarity, whereas those of Rabat are much larger and are often overturned; (c) the directions of inclination of imbricate boulders are variable at Rabat (N, NW and W), whereas they are constant in Larache (WNW); (d) the blocks were displaced for distances up to 150 m in Rabat, while the displacement of the Larache boulders was stopped by the MHW cliff; (e) the hydrodynamic equations suggest that tsunami waves, with maximum amplitudes of 5-11 m in Rabat and 4.5 m in Larache, were responsible for the displacement of the largest boulders, whereas storms may have displaced smaller ones.
This study focuses on the evolution of the Atlantic NW Moroccan Rharb continental shelf during th... more This study focuses on the evolution of the Atlantic NW Moroccan Rharb continental shelf during the Neogene and Quaternary. This region is part of a foreland basin bounded by the Rif mountain belt and thus provides an interesting geological setting to study the interactions between eustasy and tectonics and the driving mechanisms controlling stratigraphic patterns. The results are supported by an interpretation of new data including high-resolution seismic lines coupled with an interpretation of industrial seismic lines and detailed logs of industrial wells completed by micropaleontologic analysis of cuttings. The stratigraphy reveals a succession of three mega sequences related to the transition from an underfilled to an overfilled stage reflecting the long-term evolution of the foreland system. Moreover, evidence of cyclical sea-level changes are visible in the upper megasequence composed of three depositional sequences assumed to be fourth-order sequences generated in response to the most recent 100ka glacioeeustatic cycles. This study also shows the peripheral deformation of the Rharb shelf responsible for changes in the geometry of the deposits and thicknesses of the sedimentary fill during the Pliocene and Pleistocene. The most important change was triggered by the uplift of the Lallah Zahra Ridge corresponding to a major Quaternary kinematic boundary and the broad uplift of the southern shelf interpreted as a flexural uplift of the forebulge domain. The deformation-controlled sediment dispersal pattern consists of a progressive growth of the shelf accompanied with a progressive shift of depocenters from the North East to the South West and a general progradation to the North West along the southern border. This progressive filling has led to the confinement of the Rharb paleo-valley across the continental shelf. The complete filling of the palaeo-valley was followed by the development of a more than 70-m thick prodeltaic lobe at the front of the Oued Sebou river mouth during the Holocene.
SpringerPlus 2014, 3: 643-650.
Science of Tsunami …, 2008
The rocky coastline south of Rabat (Morocco) shows a large number of boulders lying upon the lith... more The rocky coastline south of Rabat (Morocco) shows a large number of boulders lying upon the lithified dune system. The boulders, of 4-100 tons, may be single, in imbricated sets, or forming clusters and ridges. Several of the boulders were lifted and overturned, thus showing pool apertures downwards. Transport distance is generally decametric because of the surface roughness, but it can reach 300 m in flat areas. All boulders have been detached from their initial position at the fractured front of the active cliff. Quantification with the help wave hydrodynamics and rock displacement mechanics shows that dislodgement and transport of these boulders were accomplished rather by tsunami than by storm waves. Although no dating was attempted, postemplacement bio-erosion by littorinids and the absence of any erosional features below the boulders suggests that they were emplaced during the 1 st November 1755 AD Lisbon tsunami.
Bulletin de l’Institut Scientifique, Rabat 34 (2012): 79-84.
Fieldwork Reports by Nadia Mhammdi
Internal report, November 2012 (Rabat/Southampton)
Internal report, February 2016 (Rabat/Southampton)
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Papers by Nadia Mhammdi
Fieldwork Reports by Nadia Mhammdi