عنوان مقاله [English]
The beach is interactions of the atmosphere, hydrosphere and lithosphere. The study area consists of highlands and hills in various forms, and includes a vast plain, called Plain Washanam, which has emerged from the erosion of the marl unit of the region. In some parts of Iran Quaternary rock type basaltic flows, marine terraces, deposits and deposits desert wind. This area is a morphodynamic region. The southern region of Sistan and Baluchestan is erosion due to the rotation of resistant and Non-resistant beds that 120-day winds the particles of erosion are easily displaced and then deposited. Considering the development of the Makran coast and the increase of construction in the region, the importance of this realization becomes more pronounced in order to reduce coastal hazards in the southern province of Sistan and Baluchestan. The main objective of this research is to study sedimentological dunes in the coasts and its impact in changing of morphological of the Oman Sea.
Matherials & Methods
The study area is located of the coastline of the north of the Oman Sea is 143 km, the borderline between the eastern of Chabahar and the Konarak in the coastal strip of the north of the Oman Sea from the station of the radio transmitter to Pasabandar. Methods of work in this research included photographing, sampling of sediment samples and measuring the morphometric components of sand dunes such as peak length, windward and backward winds. Regarding the area of sand dunes, the samples were completely randomized. So that from three point of sampling were taken. These points include of the wind direction, back wind direction and the top of sand dunes. After one sample of 500 gr was taken and transferred to the laboratory using sieve and Shaker at intervals of 0.5Ø. In the laboratory studies, samples were analyzed of grains size. Then grains sizing, drying was carried out for 15 minutes based on standard grains sizing (ASTM). In this method, the segregation of sand components from 63, 125, 250, 500, 1000, and 2000 microns was used for the 1Ø range. For this purpose, Folk method was used to determine the graining properties of sand samples. Excel 2013 software was used to plot the desired graphs such as cumulative curves and histograms. Finally, the data and information were combined and conclusions were made.
Discussion of Results
In the studied area, sand dunes, which are indicative of wind sediment, are expanded in both stabilized and unstable. The stabilized sand hills include older wind dunes, with vegetation and poor cementitiousness making the sediment particles stable. Unsaturated sand dunes contain loose and detached sediments, and ripple marks are wave brands that are low in height. The sand has a brighter color than the sand of top dunes that are easily displaced during extreme winds and storms. Sand Dunes spread in various forms along the coastal strip of the studied area, especially in the south of the villages of Konarak, Ramin, Pozm and Chabahar. Deposits mainly in the fine sand that the winds locally and also marl loosen materials and transport them to the coastal areas with the highest percentage by weight of the particles fossil of fine sand and according to folk classification, sedimentary types such as Sandy and silty sand. The results obtained from the morphoscopy confirm that the sediments of the sand dunes of the coastal environment are well-rounded.
The study of the characteristics of deposits on study area that extend with sandy sedimentary type and show a comparison of their regional features on the shores of Makran from the east to west, the size of sedimentary particles in sand dunes is reduced. The average diameter of sandstone grains is between 2 to 3 Phi with well sorted and the sedimentary type is of fine sand (0.5 Phi). The mechanism of the occurrence of these sand dunes is that formations are affected by the weathering and erosion processes of the water and wind and sediments are transported to regions of Coasts and deposited. These particles accumulate around these hindering’s and gradually increase their amount. Finally, deposition of these grains leads to the formation of sand dunes. The movement of sand dunes changes the geomorphology of the landscapes. Another important result of sedimentary features, morphoscopy, and microscopic observations of sand dunes on the southern coast of Sistan and Baluchestan province indicate that in the Makran coastal environment is that the grains size of sedimentary in the sand dunes is reduced from east to west.