پديد آورندگان :
حاضرمشار، آيدا دانشگاه آزاد اسلامي واحد تهران شمال , لك، راضيه سازمان زمين شناسي و اكتشافات معدني - پژوهشكده علوم زمين - استاديار , اسپهبد، محمدرضا دانشگاه آزاد اسلامي واحد تهران شمال - دانشيار , كهنسال قديم وند، نادر دانشگاه آزاد اسلامي واحد تهران شمال - استاديار , محمدي ويژه، مهدي دانشگاه تهران - موسسه ژئوفيزيك , محمدي ويژه، مهدي دانشگاه تهران - موسسه ژئوفيزيك , پاشازاده، بهنام دانشگاه آزاد اسلامي واحد تهران شمال
كليدواژه :
پارامترهاي آماري , رودخانه گوهررود , گسل رشت , مانداب عينك , محيط رسوبي
چكيده فارسي :
مانداب عينك در استان گيلان،غرب شهر رشت و در نزديكي رودخانه گوهر رود واقع شده است. جهت بررسي محيط رسوبي اين مانداب، تعداد 44 نمونه رسوب سطحي توسط دستگاه گرب برداشت شد. اين نمونه ها مورد آناليز دانه بندي و كاني شناسي قرار گرفتند و پارامترهاي آماري از قبيل جورشدگي، كج شدگي، كشيدگي و همچنين ميانگين اندازه ذرات محاسبه شد. مطالعات ژئوفيزيك با استفاده از 2 روش ژئو الكتريك و رادار نفوذي زمين، با هدف تعيين ساختار و عمق رسوبات، نزديكي به منشا و ميزان انرژي محيط رسوبي، بررسي حضور ناپيوستگي هاي زيرسطحي و ارتباط اين مانداب با رودخانه گوهررود صورت گرفت. نتايج دانه سنجي و پارامترهاي آماري حضور13 تيپ رسوبي با منشا رودخانه اي را در منطقه مورد مطالعه نشان مي دهد. نتايج كاني شناسي حاصل از آناليز XRD، حاكي از يك محيط رسوبي با مواد آواري است. در پروفيل هاي ژئوفيزيك مشخص گرديد كه حد فاصل مانداب با رودخانه گوهر رود ناحيه اي با مقاومت ويژه نسبي بالاست كه اين مسئله ناشي از وجود گسل رشت در حاشيه مانداب و تغيير جنس رسوبات در اين ناحيه است. بررسي پارامترهاي آماري رسوبي و مطالعات ژئوفيزيك نشان مي دهد كه مانداب عينك يك شاخه از رودخانه گوهر رود است كه توسط گسل رشت قطع شده و به شكل كنوني درآمده است.
چكيده لاتين :
Introduction
Improvement of our understanding in the environmental and geomorphological changes’ effects on
marshes and isolated waters is a critical step to address issues related to continental marshes and
their responses to these changes. Also, sedimentological studies are proper tools to interpret the
evolution of sedimentary environment (Ward et al., 1998). Additionally, to assess the ecological
impact of contamination to the environment, it is vitally important to understand the full extent and
the level of pollution into the background in the area. Regarding its capabilities in providing goods,
marshes environments are classified as the most precious ecosystems on the earth (Moreno, 2015).
Considering the effects of climate changes and human interferences, today the future of these
important landforms and ecosystems seems to be at risk and it may cause possibly irreparable
transformations (Murray et al., 2011). Also, characterizing of the composition and the
sedimentology of surface sediments is vital not only from geochemical point of view, but also from
an environmental perspective. Thus, variations in mineral compositions, trace elements and
lithogenic components should be considered as valuable tools to find out the possible sediment
sources and physico-chemical process affecting the geological records (Bernardez, 2012).
Nowadays, Eynak marsh is strictly isolated from any riverine and oceanic sediment input.
Anthropogenic effects (as an instance intense construction operation, sewage input to marsh and
etc.) likely contribute to change the circumstances and its natural habitat. Despite the importance of
this area, there is no worthy investigation devoted to the study of geophysical, mineralogical and
sedimentological signature of Eynak marsh. This investigation could be more momentous if we spot
contamination of sewage entrance from the urban areas and also underground linking to Gohar
Rood River. It is noteworthy that, Gohar Rood by itself is a fully contaminated river transporting
sewage from upstream.
Materials and Methods
Eynak Marsh is located in west of the Rasht city, North of the Guilan province. Eynak naming
comes from Persian translation of word glasses, because of similarity between glasses and aerial
photos of Eynak Marsh. Eynak Marsh is located on Gohar Rood river nearby the urban area with
dimensions of more than 2000 m in length and more than 150 m in width.
To study the sedimentary environment of the Eynak Marsh, 44 surface sediment samples were
collected using a sediment sampling device (Van Ween Grab). Afterward, on the lab, samples were Finally, we research the sediments of the lake terraces in the area and based on the particle average
depends on source type of deposition, transport factor type and deposition conditions. Sediments
and indexes show energy conditions in layers. As a result, these terraces confirm the lake-margin
sediments conditions with an average of small to medium sandy survey.
Conclusions
Evidence indicates that there have been a relatively shallow lake in the past and low energy
environment and it is affected by evaporation and drying conditions, alternatively. As well as
different levels of terraces with different heights shows the advance and retreat phases of the lake.
