شاخص‌هاي فيزيكوشيميايي موثر بر رسوب‌‌‌زايي مارن‌هاي پهنه زمين‌ساختي زاگرس، مطالعه موردي: استان چهارمحال ‌و بختياري

Effective physico-chemical indices on marls sediment yield in Zagros structural zone, case study: Chaharmahal and Bakhtiari Province

ﻣﺎرن ﻫﺎ ﯾﮑﯽ از ﻋﻮاﻣﻞ اﺻﻠﯽ رﺳﻮب زاﯾﯽ و ﻣﺘﻌﺎﻗﺐ آن ﻓﺮﺳﺎﯾﺶ ﺧﺎك در ﺣﻮزه ﻫﺎي آﺑﺨﯿﺰ ﺑﺸﻤﺎر ﻣﯽ روﻧﺪ. ﺗﺤﻘﯿﻘﺎت ﻧﺸﺎن ﻣﯽ دﻫﺪ ﮐﻪ ﺑﯿﻦ ﻣﯿﺰان رﺳﻮب زاﯾﯽ ﻣﺎرن‌ﻫﺎ ﺑﺎ وﯾﮋﮔﯽ ﻫﺎي ﻓﯿﺰﯾﮑﯽ و ﺷﯿﻤﯿﺎﯾﯽ آنﻫﺎ ارﺗﺒﺎط ﻣﻌﻨﯽ داري وﺟﻮد دارد. ﺑﺎ ﻫﺪف ﺗﻌﯿﯿﻦ ﮔﺴﺘﺮش ﺳﺎزﻧﺪﻫﺎي ﻣﺎرﻧﯽ از ﯾﮑﺴﻮ و ارزﯾﺎﺑﯽ ﮐﻤﯽ ﺗﺎﺛﯿﺮ ﺷﺎﺧﺺ ﻫﺎي ﻣﺬﮐﻮر در ﻣﯿﺰان رﺳﻮب زاﯾﯽ ﻣﺎرن ﻫﺎي اﺳﺘﺎن ﭼﻬﺎرﻣﺤﺎل و ﺑﺨﺘﯿﺎري، ﺗﺤﻘﯿﻖ ﺟﺎﻣﻌﯽ ﺻﻮرت ﭘﺬﯾﺮﻓﺖ. در اﯾﻦ ﭘﮋوﻫﺶ، ﭘﺲ از ﺷﻨﺎﺳﺎﯾﯽ و ﺗﻔﮑﯿﮏ ﭼﯿﻨﻪ ﺷﻨﺎﺳﯽ ﺳﺎزﻧﺪﻫﺎي ﻣﺎرﻧﯽ اﺳﺘﺎن و اﻧﺠﺎم ﻧﻤﻮﻧﻪ ﺑﺮداري ﻫﺎي ﺳﯿﺴﺘﻤﺎﺗﯿﮏ، آزﻣﺎﯾﺶ ﻫﺎي ﮐﺎﻧﯽ ﺷﻨﺎﺳﯽ )XRD(، ﻓﯿﺰﯾﮑﯽ و ﺷﯿﻤﯿﺎﯾﯽ ﻻزم، اﻧﺠﺎم و ﻧﺘﺎﯾﺞ ﺑﺎ اﺳﺘﻔﺎده از روش ﻫﺎي آﻣﺎري ﺗﺠﺰﯾﻪ و ﺗﺤﻠﯿﻞ ﺷﺪﻧﺪ. در اداﻣﻪ، ﺑﺎ اﺳﺘﻔﺎده از ﺑﺎران ﺳﺎز ﻗﺎﺑﻞ ﺣﻤﻞ در ﺻﺤﺮا، ﻣﯿﺰان رﺳﻮب زاﯾﯽ ﻫﺮ ﯾﮏ از واﺣﺪﻫﺎي ﭼﯿﻨﻪ ﺷﻨﺎﺳﯽ ﻣﺎرﻧﯽ اﻧﺪازهﮔﯿﺮي ﺷﺪ. ﻣﺠﻤﻮﻋﺎً 1073/95 ﮐﯿﻠﻮﻣﺘﺮ ﻣﺮﺑﻊ ﻣﻌﺎدل 6/5 درﺻﺪ از ﻣﺴﺎﺣﺖ اﺳﺘﺎن را واﺣﺪﻫﺎي ﭼﯿﻨﻪ ﺷﻨﺎﺧﺘﯽ ﻣﺎرﻧﯽ اﺷﻐﺎل ﮐﺮده اﺳﺖ. از دﯾﺪﮔﺎه رﺳﻮب زاﯾﯽ، ﺳﺎزﻧﺪ رازك ﺑﺎ ﻣﯿﺎﻧﮕﯿﻦ 96/34 ﮔﺮم ﺑﺮ ﻣﺘﺮ ﻣﺮﺑﻊ در رﺗﺒﻪ اول و ﺳﭙﺲ، ﺳﺎزﻧﺪﻫﺎي ﭘﺎﺑﺪه، ﻫﺮﻣﺰ، ﻣﯿﺸﺎن و ﮔﻮرﭘﯽ ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﺎ 87/1 ،94/41، 76/17 و 33 ﮔﺮم ﺑﺮ ﻣﺘﺮ ﻣﺮﺑﻊ رﺳﻮب ﺗﻮﻟﯿﺪي در رﺗﺒﻪﻫﺎي ﺑﻌﺪي رﺳﻮب زاﯾﯽ ﻗﺮار ﻣﯽ ﮔﯿﺮﻧﺪ. ﻧﺘﺎﯾﺞ ﻫﻤﺒﺴﺘﮕﯽ ﺑﯿﻦ ﺑﺎﻓﺖ ﺧﺎك و ﺗﻮﻟﯿﺪ رﺳﻮب ﺣﮑﺎﯾﺖ از ﻫﻤﺒﺴﺘﮕﯽ ﻣﺜﺒﺖ ﻣﻌﻨﯽ دار ﻣﯿﺰان ﺳﯿﻠﺖ، آﻫﮏ ﻓﻌﺎل و ﺳﺪﯾﻢ ﺗﺒﺎدﻟﯽ و ﻫﻤﺒﺴﺘﮕﯽ ﻣﻨﻔﯽ ﻣﻌﻨﯽ دار ﻣﻘﺪار رس ﺑﺎ رﺳﻮب زاﯾﯽ دارد. ﺣﻀﻮر ﮐﺎﻧﯽ ﻫﺎي رﺳﯽ ﮐﺎﺋﻮﻟﯿﻨﯿﺖ و اﯾﻠﯿﺖ از ﻋﻮاﻣﻞ ﺗﺸﺪﯾﺪ رﺳﻮب زاﯾﯽ در ﺳﺎزﻧﺪﻫﺎي ﻣﺎرﻧﯽ ﺑﺸﻤﺎر ﻣﯽ روﻧﺪ.

Marls are one of the main causes of sediment production and subsequent soil erosion in watersheds. Researchs shows that there is a close relationship between the rate of marls sediment yield and their physical and chemical characteristics. With the aim of determining the expansion of marly formations and a quantitative assessment of the mentioned indices role on the sediment yield of marls in Chaharmahal and Bakhtiari Province, a comprehensive study was conducted and its outstanding results are presented in this study. After identifying and separating the marly formations in Chaharmahal and Bakhtiari Province and performing systematic sampling, necessary physical and chemical experiments were performed and the results were analyzed using statistical methods. Then, using a rainfall simulator, the sediment production rate of each marly stratigraphic units was measured in the field. Results showed that about 1073.95 Km2 (equal to 6.5%) of province rocks has devoted to marly lithological units. On the basis of analyses, Razak, Pabdeh, Hormoz, Mishan and Gurpi formations with mean of 96.34, 94.41, 87.1, 76.17 and 33 grm-2 are the most sensitive marly formations, respectively. Sediment yield is directly related to silt amounts, total lime, active lime, exchangable sodium and reverse related to clay amounts. The presence of Kaolinite and Illite clay minerals is one of the intensifying factors in sedimen yeild in marly formations.