The Mesopotamian Sedimentology researches..

Sedimentological and mineralogical study of rocky islands in Khor Al-Zubair – north west of the Arabian Gulf

Saeed Omar Wasel

University of Hudaida

Hudaida – Yamin

(E-mail: waselsaeed@yahoo.com)

Abstract

   The study area represents the rocky island stations, situated to the north and other station to the south of Khor Al-Zubair port , north west of the Arabian Gulf. The area is a tidal flat with gentle slope toward the sea. Sixty samples were collected from two stations in different depths 0.5,  1 and 1.5 m from ground surface, moreover, ten samples have been chosen from the rocky island. The sampling was carried out during Nov. 2001 to July 2002 by using grab sampler and hand auger and corer. Grain size analysis, mineral identification, carbonate percentage, and organic carbon percentage were obtained. Petrographic studies, and scanning electron microscope have been done for the rocky samples. Grain-size analysis shows that the Khor Al-Zubair sediments composed of silty clay and sand deposits restricted in the rocky area. Statistical grain size parameters stated also two groups of sediments, fine-grained sediments characterized by very poorly to poorly sorted, symmetrical to very coarse skewed, and platy kurtic. And coarse sediments characterized by very poorly to poorly sorted, symmetrical to very fine skewed and leptokurtic. These variations in statistical grain size parameters explain the high influence of hydrodynamic conditions dominated during the period of deposition. The percentage of carbonate content is 15.92-39.24% and organic carbon 0.09-0.48%, the higher values are concentrated in fine fraction sediments and vice versa. The opaque minerals, pyroxene, hornblende and epidote are the major constituents of the heavy minerals. The garnet, zircon and tourmaline are dominant, whereas, chlorite, staurolite and rutile present in minor quantity. Other present in trace minerals such as; kyanite, biotite and titanite. This assemblage of minerals provide the origin of Mesopotamian plain sediments and the erosion of neighboring outcrops of formations. The quartz is the  major constituent of light minerals, its grains are rounded to subrounded  monocrystalline  with few percentage of polycrystalline grains. The quartz is followed by carbonates in the major constituent of light minerals. The feldspar ( orthoclase and plagioclase) is abundant in the light minerals. Petrographic studies show the texture and minerals of rocks which are composed of quartz, feldspar and rock fragments, cemented by micrite of high Mg-calcite. No lateral distribution of rocks near the coast, moreover, the layers dip toward the sea and the mineral assemblages in the layers are highly different. These observations indicate that the rocks represent beach rocks formed by hydrodynamic processes, which supply the sands from the neighboring area.

Unpublished M.Sc. Thesis, University of Basrah, College of Science, 2003