Granulometric Analysis and Environtment of Deposits of Surface Sediments of the Marchica Lagoon (North-East of Morocco)

Abstract

The Marchica lagoon is located at the eastern end of the Moroccan Oriental Rif. Which constitutes a zone of encounter between the rifain and atlasic geological systems. Such a zone is characterized by small mountains which dominate wide depressions more or less flat and open on the Mediterranean. These geological units are drained by a network of streams that feed the Marchica lagoon and neighboring coastal areas into a detrital product of different kinds. The granulometric analyzes carried out on the surface sediments of the lagoon of Marchica made it possible to characterize in detail the granulometry of the current sedimentary cover after the opening of the new pass and to establish the spatial variations of these granulometric fractions. The following conclusions can be drawn from the analyzes: The sand contents vary between (14.6 and 77.7%), the highest content is recorded at the site of Chaâla and near the new pass; It is a sandy fraction rich in shellfish debris of gastropods. The fine silt contents vary between (0 and 20%), the highest content is recorded in the center of the lagoon. The highest proportions of coarse silt (60.4 and 52.65%) are recorded respectively at Kariat stations and at the center of the lagoon. This fraction is rich in woody debris from halophilic plants. The proportions of the clays are on average between 8 and 15%, the large proportions are recorded in the zones which can be considered as quiet depressions with low hydrodynamism favoring sedimentation by decantation and flocculation of the clays. It is a very evolved vase deposited in a calm environment by excess of charge without subsequent rearrangement. This study resulted in a sediment distribution, as well as a determination of the environment of sediment deposition.