TEXTURAL ANALYSIS AND SHAPE CHARACTERISTICS
OF QUARTZ GRAINS OF THE COASTAL SEDIMENTS IN
THE AREA BETWEEN HURGHADA AND ELQUSIER, RED
SEA COAST, EGYPT
YOUSRIA M. SAMY
National Research Center |
Textural analysis of the coastal sediments between Hurghada and El- Qusier show that the investigated sediments have a relatively small range of grain size. The coarse, medium and fine sand fractions form about 87% of the average grain size distribution.
The coastal sediments are characterized by the presence of coarse tail of coarse and very coarse sand (rolling populations) which means that such sediments arc not typical beach sediments. Cumulative probability curves of the sediments exhibit general unimodal pattern even after removing of carbonates.
The statistical grain size parameters show that the sediments are well sorted to poorly sorted, very negatively to positively skewed and vary from very platykurtic to very leptokurtic in characters.
The presence of carbonate contents don’t greatlv affect the grain size picture and the sorting of the sediments. The results obtained from the textural analysis indicate that the studied coastal sediments are not typical beach sediments (i.e. formed mainly through beach processes). They constitute moderately to poorly-sorted immature alluvial sediments derived from neighboring country rocks and transported through wadis during rainy periods.
The shape analysis and the calculated mean roundness values for the sediments indicate that there is a general improvement of roundness northward along the coast. This observation is recorded for all the studied size classes.
The surf ace texture of the quartz grains as revealed from the SEM are characterized by the prevalence of rnechanical features rather than chemical ones. The mechanical features reflect the effect of both sub-aqueous and aeolian origin. The sub-aqueous origin is supported by the presence of v-shaped pits, conchoidal fractures and curved grooves, whereas the aeolian effects are related to the presence of upturned plates, meandering ridges and graded arcs. The presence of aeolian features which is probably a relict from aeolian environment in such coastal sediments may suggest that some aeolian sands were reworked by waves and tides to form these coastal sediments.
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