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Sedimentary Facies and Depositional Environment of Oligo-Miocene of the Southern Shore of the Strait of Gibraltar (Rif, Morocco)

Salhi Fouad, El Khalidi Khalid, Zourarah Bendahhou

Ecological Engineering & Environmental Technology

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2024

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Vol. 25, iss. 3

233--252

EN

This paper highlights a detailed sedimentological investigation of the deposits of Oligo-Miocene age on the southern shore of the Strait of Gibraltar commonly called flyschs Numidian, micaceous-sandstone flysch of Beni Ider and merinid flysch. This study has allowed us to demonstrate the existence of different facies and environments linked to the different processes that prevail in the Maghrebian basin under the simultaneous control of sedimentary input, eustatism and the tectonic process. Our study is based on the observation and the detailed stratonomic analysis of the different facies encountered in the Oligo-Miocene age series of flyschs from the southern shore of the Strait of Gibraltar. For the first time, this analysis shows that the Numidian successions studied, except that of Oued Lihoud, were deposited in deltaic environments (deltaic cone) at the level of the North African margin (Rif chain). These are prodelta deposits where slides, slumps or turbidites of predominantly fluvial delta fronts, regular waves and storm waves, fluvial and estuarine channels and tidal plains are sometimes intercalated. The micaceoussandstone flyschs are due to gravitational sedimentation at the level of the submarine plain of the Maghreb basin. We have identified different categories of deposits: low, medium and high density turbidites, pulsation turbidites, homogenites, debris-flows and contourites. The Merinid flyschs are also due to mixed gravity sedimentation from a lithological point of view between the Numidian sandstones and the micaceous-sandstoneof Beni Ider. These deposits have therefore occupied an intermediate position between the southern and northern margins of the Maghrebian basin. In addition to the gravity facies, the deposits show high-density megaturbidites. This study also allowed the identification a major eustatic decline that was recorded during the Oligocene, the cold climate of the Oligocene and distensive (north) and compressive (south) tectonic movements depending on the position in the basin.

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Potential Energy Power from Tidal Current in Lagoon System – The Case of Oualidia Lagoon, Morocco

Bouchkara Mohammed, Siagian Hendry, Chahid Nouhaila Erraji, Joudar Imane, Hajjaj Charaf, Benazzouz Aïssa, Zourarah Bendahhou, El Khalidi Khalid

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 4

116--127

EN

The lagoon is a natural system protected from the sea by a dune barrier creating energy from the movement of rising and falling tides, thus providing a sustainable option for extracting energy from tidal currents. The energy that can be extracted is one of the most potential renewable energy sources. Therefore, the interaction of tidal currents with stratification layers has become important to optimize the efficiency of energy conversion at each depth layer in water masses. We have chosen as a case study, the Oualidia lagoon (Atlantic coast of Morocco). This ecosystem is characterized by hydrodynamics relatively favored by tides and tidal currents which are the main intra-lagoon currents, with a predominance of the semi-diurnal component M2 (period of 12 h 25) with 2.1 to 3.4 m of tidal range. The Multicell Argonaut-XR ADCP is used to measure the current velocity in the Oualidia lagoon at three different stations to study tidal patterns in a vertical layer of water depth. At each station, current velocities were recorded in each 0.5 m layer over a depth of about 5 m. As a result, this study showed that current velocity measurements to be used as renewable energy are found at station 1 located at a depth of 3.5 meters (~layer 5) with a current velocity of 0.771 m/s and a power density value of 235.344 W/m2, station 2 located at a depth of 3.5 meters (~layer 5) with a current velocity of 0.4 m/s and a power density value of 32.86 W/m2 and station 3 is located at a depth of 3 meters (~layer 6) with a current velocity of 0.527 m/s and a power density value of 75.157 W/m2. The variation in current velocities between the different stations is mainly influenced by tides (Flood/ebb), the period of the measurements and the location of the stations. This work presents a model for extracting electrical energy through the use of tidal and current flow variations in such semi-enclosed natural system including lagoons.

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Periodical Morphodynamic Changes of Sand Movements at El Jadida Beach

Bourhili Amine, El Khalidi Khalid, Minoubi Abdenaim, Maanan Mehdi, Zourarah Bendahhou

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 4

15--26

EN

El Jadida Beach (X: -8.5007116; Y: 33.2316326) is a sandy beach of low altitude that constitutes a kind of enclave located between the port of El Jadida and rocky outcrops. It is influenced by natural and anthropic factors, as well as the impact of tourism, particularly during the summer, when sand is used for amusement activities (Beach Ball competition). In order to follow the morphodynamic changes of this beach, we carried out a study on two different time scales: a fifty-five years (1963 – 2018) shoreline evolution study using aerial photos and satellite images based on GIS tools using the Digital Shoreline Analysis System (DSAS) and a two-years (2017–2019) morphological beach study using a Differential Global Positioning System (DGPS). According to the results obtained by the diachronic study, the beach studied showed erosion in its middle and an accumulation at these bulges. This result is due to the presence of the harbor breakwater to the NW and the rocky outcrops to the SE; acting as a barrier preventing the movement of sediments and the erosion in the middle can be explained by the reduction of the sediment supply from the Oued Oum Erabia and by the exposure of this part to the dominant swells and also the human activities like used the beach for amusement activities (Beach Ball competition and other). Beach profile observations results show accumulation in the subaerial beach and erosion in the lower part of the foreshore. The study on two different time scales adopted in this paper, allowed us to understand longshore and cross-shore sedimentary mobility.