Hamid Reza Peyrowan; Amir Samadi Tabrizi; Samad Shadfar; Ahmad Motamed
Abstract
Marl formations are widespread in Iran. High potential to erodibility of marl formations in watershed basins of Iran cause many problems including loss of soil quality in agricultural and pasture lands and forests, increasing the risk of landslides and mass movements, reducing the quality of ground and ...
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Marl formations are widespread in Iran. High potential to erodibility of marl formations in watershed basins of Iran cause many problems including loss of soil quality in agricultural and pasture lands and forests, increasing the risk of landslides and mass movements, reducing the quality of ground and surface water, sediment load increases entered into the reservoirs, desertification areas due to intensive erosion and watershed management plan failure due to inadequate knowledge of the susceptibility to erosion the formations. The study area, Gatchab and Siahkooh Mountains situated in the northwest of central playa of Iran (Kavir plain). It is located in southwest of the Semnan city with 74 km distance. The widespread of the geological unit in the area is upper red formation with three members M1, M2 and M3. With respect to sedimentology finding on textures of Neogene sediments, they are sandy silt, silt, sandy mud and mud particles. The examination of distribution of various particle size of the sediments have shown that these sediments deposited in shallow water and lagoonal environments with changing of the depth, that changed to high dynamic environments condition of channel rivers. The results of analyses have shown that the percent abundance of lime in these sediments change from 24.28% to 34.98%. Because of the low contents of lime compound and clay particles, it is better to called them salty and gypsiferous siltstone and mudstone instead the marl term for these sediments.
Amir Samadi Tabrizi; Hamid Reza Peyrowan; Ahmad Motamed
Abstract
This study is about the relation between erodibility rate and plasticity features ofNeogene Marl deposits of Gatchab and Gitcha in southeast of Garmsar. The erosions alfeature of Neogene sediments are rill, gully and waterway shapes. The depth of soilsampling for rill and waterway types is from surface ...
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This study is about the relation between erodibility rate and plasticity features ofNeogene Marl deposits of Gatchab and Gitcha in southeast of Garmsar. The erosions alfeature of Neogene sediments are rill, gully and waterway shapes. The depth of soilsampling for rill and waterway types is from surface to 30-centimeter thickness and forgully one is from head cut and all outcrop of gully bank. The engineering analyses forsediments include liquid limit, plastic limit and plastic index and engineeringgranulometry. On the basis of engineering classification of soil, the sediment ofGatchab and Siahkoh mountains are fine grained soils with low to very low degreecohesive, consequently low plastic limit and low internal consistency. The comparisonof the results between marl units of Gatchab and Gitcha area have shown the M2 unithas low plasticity and high sensitive to erosion to other units M1 and M2. By the way,the M1 unit is high resistance to water erosion in comparison to M3 unit. From allaspect, Abundance of the lime and clay particle amounts is positive effects ondecreasing of sensitivity rate to erosion of Neogene deposits. The above mentionedresults base on plasticity features of Neogene deposits confirmed by field witness.
