Grain size distribution and environmental implications of Rosetta beach, Mediterranean Sea coast, Egypt

Abstract

Grain-size analysis of beach sediments along Rosetta beach of the Nile delta coast has been carried out to reveal the depositional environment condition, energy and hydrodynamic conditions, as well as the mode of transportation along the study area. In total 56 beach samples were collected, distributed along 3 profiles parallel to the shoreline and covering the shoreline, semi-wet area, and the dry backshore area. The study showed the great sensitivity of the interrelationships of various grain size statistical parameters (mean size, sorting, skewness, and kurtosis) to the slight variations in the compositional formula of the sediment mixture. Distribution of the textural parameters revealed the dominance of unimodal pure sand sediments, mainly Nile sand sources. The fluctuation between moderately well-sorted to well-sorted sediments and from coarse skewed to fine skewed under leptokurtic to platykurtic nature was distinguished at different localities and relevant environmental implications. Different discrimination tools as bivariate cross plot of grain size parameters, Linear Discrimination Functions (LDF), skewness and kurtosis relationship as a non-dimensional expression of sediment/energy simulation, Energy Process diagram, and mode of transportation (C-M diagram), indicates the marine signature followed the riverine input as a function of the sediments locality. Depositional processes were mainly hydraulically controlled through active energy processes of the marine environment. The fluvial nature of sediment demonstrated the graded suspension and saltation modes as the prime factors for transportation, influenced by marine and turbidity environment actions, within a shallow agitated marine environment.