تجزيه و تحليل مورفوژنز و تفاوت‎‎هاي كمّي و كيفي مخروط‎افكنه‎‎هاي رشته‎كوه بينالود با رويكرد هيدرومورفوتكتونيكي

Morphogeno Analysis of Qualitative and Quantitative Differences of Alluvial Cones of Binaloud Mountains with Hydromorphotectonic Approach

رشته‎كوه بينالود يك سيستم چين‎خورده‎ي تراستي است كه در شمال‎شرق ايران واقع شده و افزون‎بر فرايند‎هاي آغازين و حركات دامنه‎اي، فرايند‎هاي جرياني و رودخانه‎اي آن را دگرگون‎كرده و لندفرم‎‎هاي آبي گوناگون و متعدّدي را، چه در پيكره‎ي كوهستان و چه در نقاط پايكوهي و دشت‎‎هاي مجاورش خلق كرده است. يكي از بارزترين و مهم‎ترين لندفرم‎‎ها‎ي بيان‎شده، شكل‎گيري مخروط‎افكنه‎‎هاي متنوّع در پايكوه‎‎هاي شمالي و جنوبي بينالود است كه از ديدگاه منشا و ژنز، شكل و ابعاد كمّي (تعداد، وسعت، و...) تفاوت‎‎هاي بارز و آشكاري را از خود نشان مي‎دهند. اين تفاوت‎‎هاي ژيومورفولوژيكي مخروط‎افكنه‎‎هاي شمالي و جنوبي بينالود، معلول دخالت عوامل و عناصر هيدرومورفوتكتونيكي بوده و در پتانسيل‎‎ها و تنگنا‎هاي محيطي، پيدايش و تعدّد سكونتگاه‎‎هاي شهري و روستايي و نيز، فعّاليّت‎‎هاي وابسته به آنها تاثيرگذار بوده است. ازجمله اينكه مخروط‎افكنه‎‎هاي دامنه‎ي شمالي، از نظر كشاورزي داراي منابع آب و خاك فراوان و مطلوب بوده، درحالي‎كه مخروط‎افكنه‎‎هاي دامنه‎ي جنوبي دچار تقطيع شده و اين قطعه‎قطعه‎شدن و كوچكتر بودن مخروط‎‎هاي مذكور، مانع هرگونه فعّاليّت مي‎شود. بنابراين شناخت مخروط‎افكنه‎‎هاي منطقه، هم از ديدگاه پژوهش‎هاي بنيادي و هم از ديدگاه برنامه‎ريزي محيطي، امري ضروري و مهم به‎شمار مي‎آيد. از اين رو، پژوهش پيش رو برپايه‎ي روش تاريخي و به‎ويژه، روش تجربي بوده و بر اساس آن به واكاوي مساله پرداخته است. در راستاي انجام اين پژوهش و رسيدن به اهداف آن، هم‎زمان با انجام عمليّات ميداني و آزمايشگاهي و كارگاهي (مانند تفسير اسناد جغرافيايي و گرانولومتري) از مدل‎‎هاي ژيومورفولوژيكي (استرالر) و نرم‎افزار‎هاي GIS، ArcGIS هم استفاده شده است. نتايج به‎دست‎آمده نشان مي‎دهد كه عوامل گوناگوني در بروز تفاوت‎‎هاي ژيومورفولوژيكي مخروط‎افكنه‎‎هاي شمالي و جنوبي بينالود تاثيرگذار بوده و در اين ميان عوامل تكتونيكي (چين خوردگي‎‎هاي تراستي بينالود ) و عوامل هيدرومورفوتكتونيكي بيشترين نقش را داشته‎اند.

Extended Abstract Introduction Flow and river processes are one of exogenous factors causing genesis and change of some roughness such as alluvial cones. Alluvial cones are one of erosive cumulative landforms of flow processes and in addition to a set of potentials such as fertile soils and rich surface and ground waters and etc, they have some geomorphologic dangers and bottlenecks such as land intersection and embankment and etc. Since many rural and urban dwellings are placed on alluvial cones, they face with such potentials and bottlenecks so comprehensive and close study and identification of alluvial cones are necessary genetically and practically. In addition to geomorphic dangers and potentials, alluvial cones of Binalood northern and southern hillsides have apparent differences and asymmetries. Thus it is necessary to study and analyze these differences. Methodology In the present research, experimental method ad historical view were used and descriptive and analytical methods based on apriori method and some geomorphologic models such as Straller and granulometric and morphoscopic operation were employed for qualitative and quantitative analyses. In addition to field studies, experimental and library studies were also performed and variety of topographic and geologic maps and air photographs and software gis, arc-gis-Excell were employed. Geologically, Binalood northern hillside has mainly formed from filit however southern hillside although has filit, calcic constituents are also present. Climatically, the area studied is of cold and semi arid climate and its annual precipitation is about 320mm. Hydrologically, there are 69 small and large basins and a number of natural and artificial lakes in northern hillside so it has more water tables than southern hillside because southern basins are fewer, smaller and more limited. In view of soil and vegetation, the respective area is very weak and soils are mostly stony and from lithosol type especially on filit constituents. Results and Discussion In addition to apparent differences in alluvial cones of the area, there are slight differences in them. For example, according to above reasons and arguments, first extent, thickness and depth of alluviums and sediments in Binalood northern alluvial cones are higher. Secondly, from granulometric viewpoint, there are apparent differences between them so granulation of sediments formed by northern alluvial cones is finer and more homogenous because these grains have became finer and pulverized by traveling more distance through longer rivers and more fragile structures. Third, from morphoscopic view, rounding coefficient in grains of northern alluvial cones sediments is higher because of the reasons mentioned. However, because there are schist layers in this front, some grains are round and flat rather than round and circular. Final result is that because number and extent and thickness and depth in Binalood northern alluvial cones are higher and granulation is finer, there are more susceptible and fertile soils and their ground and surface waters are richer. So more important urban and rural residences have been created in hillsides of this area and more cultivated lands have been kexpanded. However, from geomorphic hazards and bottlenecks viewpoint, Binalood southern alluvial cones have limited conditions for agriculture due to few number and low extent and coarser sediment grains. Secondly, because faults are in the vicinity of these alluvial cones, intersection of alluvial cones and probability of earthquake in these surfaces are more than Binalood northern alluvial cones Conclusion With a glance to topographic and geologic maps especially satellite photographs of Binalood area, it can be seen that there are many different and wider alluvial cones in Binalood northern and northern east hillsides and fewer and so smaller alluvial cones in Binalood southern and southern west hillsides. These differences are very obvious, distinct and distinguishable easily which raise questions. What is indisputable is that natural and environmental conditions (climatologic, hydrologic, geobotanic, lithologic, tectonic and …. properties) play a role in genesis of these alluvial cones and existing differences between them however, hydromorphotectonic (tectonic and hydrogeomorphic factors) conditions are more important than others because these conditions affect both on formation of alluvial cones and their differences directly and on abovementioned natural and environmental conditions indirectly.