The effect of active tectonic to morphology of Derakt -Tangan river fan of shahdad in Kerman

Somayyeh Sadat Shahzeidi Geography department. Isfahan

University Isfahan, Iran

S_shahzeidi@yahoo

Mojgan Entezari Geography department. Isfahan

University Isfahan, Iran

M.H Ramesht Geography department. Isfahan

University Isfahan, Iran

Abstract— The alluvial fan of the Shahdad in Derakt – Tangan River is one of the biggest alluvial in total dry area in the North- North Eastern Kerman. This alluvial fan is formed effected by different materials erosion in drainage basin of Derakt–Tangan River and laying these materials in the final part of this drainage basin called Loot. Tectonics activate with efficacy in the place of the settlement of the alluvial fan. The region, which is being studied, is one of the active tectonic regions. The severe tectonic activities in the studing region have been proved by several observations . One of the most important evidences in the region is the various faults in the area and implies to fan alluvium (from head to end), study line profile in past and present. The most important fault of the region is the great fault of “Nay band“,the southern fault of “shahdad “ and the series of faults having the direction of “North–western to South-Eastern and Northern and Southern".The aim of this article is The morphology of Derakt – Tangan river fan indicative on neotectonics in the region.

Keywords- Alluvial fan of the Shahdad; Active tectonic; Morph of fan; Effect of faults

I. INTRODUCTION Geomorphologic studies show that there is an organic

relationship between climate, tectonic and landforms of the earth. This relationship is so high that the Geomorphology scientists believe that geomorphologic phenomena are acquired through internal and external formation power [14].

Many studies at different scales and using modeling or observation, showed that alluvial fan plays a key role in various place and climate. Alluvial fans are gently sloping, fan-shaped landforms are created over time by deposition of eroded sediment, and they are common at the base of mountain ranges in arid and semiarid regions. About this subject at first we should Recognize and characterize alluvial fan landforms and second Define the nature of the alluvial fan environment and identifying active and inactive components of the fan [7], then continue. Many researchers tried to create some models for show tectonic activities and manage this place.

I. Background of study There are many different studies about the alluvial fan

and effects Active tectonic. Al-Sarawi, studied Morphology and features of alluvial fans in Kadhmah Bay and indicated that there is a good interrelationship between morphology

and features [1]. Bull investigated alluvial fans and near-surface subsidence in western Fresno County, California [3]. Beaty searched debris flow, alluvial fans and a revitalized catastrophism [4]. Catto researched morphology and development of an alluvial fan in a permafrost region [5] and Clarke studied Neotectonics and stream piracy on the Lytle Creek Alluvial Fan, Southern California [6]. Gerson et al analyse Indicators of faulting events and periods of quiescence in desert alluvial Fans [8]. The other groups of alluvial fan found Techniques for measuring rock weathering[11] , The influence of debris flow rheology on fan morphology Owens Valley [12], and Geomorphic controls of alluvial fan deposition in the Sonoran Desert [13] .In Iran Arzani researched the fluvial mega fan of Abarkoh Basin(Central Iran)[ 2] .

II. INTRODUCTION

A. Methodology First of all, the authors of this paper investigated the air

photographs and field studies to find the place of the alluvial fan of the Shahdad in East of Kerman on DEM of province using Software Arc GIS 9.3 (digital altitudinal model with 85m cellular size gained from the digital photos of radar). Therefore In order to determine the position of the fan and neighboring, separated boundary of fan. Finally, after analyzing map, calculating the extent of basin and alluvial fan. We found some result about main fault and relate it to morphology of fans.

B. The tectonic activities and several evidences The Derakt – Tangan River fan is in the active tectonic

region and features of alluvial fans formed with “ Nayband fault and the series of faults having the direction of “North–western to South-Eastern and Northern and Southern". The drainage basin of alluvial fan leads from East to “Kavir-loot“and loot is one of the paleo lake that we see it now. In this field, Highest elevation is 3800 meters and lowest is 370 meters around the Loot Fig 1.

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2011 2nd International Conference on Environmental Science and Technology IPCBEE vol.6 (2011) © (2011) IACSIT Press, Singapore

Fig 1. Location of Alluvial fan of Kerman province

In palaeogene organic area in west of “Nayband

fault“,exactly on head of the alluvial fan, mountain front started to uplift and west of the fault up down . Continuous movements has been caused that in neogen phases of land was changed and created two different levels , we called this upland and low land .Afterwards alluvial fan features was trend similar this time[10] ( Fig 2).

(Fig 2) alluvial fan features

Tectonic movement was high and effected on geology formation. We investigated geology map (Index: 1/250000, 1/100000) of studied case and separated to2 part. one part consist wide and vast plain which was covered with

Quaternary alluvial deposits, Aeolians , sand dunes, around the Loot and the second part contains elevation that cover with hard formation and little thin alluvial area. Geology sequence is existed from Precambrian formation to Quaternary .The main important stones in this region are limestone, sandstone, shale and conglomerate. Recent and active tectonic movements in the studied region have been proved by other several observations. Geologist and geomorphologist find some ways to show tectonic activities, so we explain some of them that Contains to: [9]

1-Ratio of valley –floor width to valley height: Vf=2Vfw [(Eld- Esc) +(Erd- Esc)]

where (Vf) is the valley- floor width – to heigh ratio , (Vfw) is the width of valley floor, (Eld and Erd) are elevations of the left and right valley divides , (Esc) is the elevation of the valley floor. (Vf) values are different : (Vf) <1 tectonic is very active and show increasing uplift rates , .( Vf)between 1-2 semi active , .( Vf)>2 low uplift rates. 2-Mountain –front sinuosity: Smf = Lmf /Ls

Where ( Smf ) is the mountain – front sinuosity , (Lmf) is the length of mountain front along the foot of the mountain , at the pronounced break in slope. Value near 1 shows uplift and active tectonic . 3-Drainage basin asymmetry: AF =100(Ar/At)

Ar: is the area of the basin to the right (facing downstream) of trunk stream, At: is the total area of drainage basin , Af: should equal about 50 . The AF is sensitive to tilting perpendicular to the trend of the trunk stream. Values of AF greater or less than 50 may suggest tilt.( AF > 50 implies tilt down to the left of basin)

TABLE1- TABLE OF VALUES OF EQUATION

(SHOW ACTIVE, SEIMI ACTIVE AND NONE ACTIVITY)

Measurement methods

conclusion Equation

Between 1.1 -1.45 (Active)

S=Lmf/Ls

)Active ( 68.98

AF =100(Ar/At)

.Between 0.5 -1.04 (Active and in some place semi active)

Vf=2Vfw [(Eld- Esc) + (Erd- Esc)]

4- The hypsometric integral

Quantitative analysis of topography can be done with landscapes at any scale, from a single drainage basin to the

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entire planet. Comparing the results from different areas, however, can be difficult without some technique for removing the effects of scale. The hypsometric curve is a graph of area-altitude distribution that is dimensionless, meaning that it factors out both the total size of the area being studied and the total amount of relief. The hypsometric curve is a plot of relative height (h/H) versus relative area (a/A), you can compare different areas in order to study the effects of different bedrock types, different plate tectonic settings, or the balance between tectonics and erosion. The hypsometric curve of the drainage basin of alluvial fan of the Shahdad in Derakt – Tangan River is in Figure3. It shows that tectonics conquest to erosion (Fig 3)

(Fig 3) Hypsometric integral of drainage basin of The

Derakt – Tangan River fan

C. Morphology of alluvial fan can result of 3 reasons: 1- The “Nayband fault “.(Fig 5) 2- The southern fault of “shahdad “: This fault change

morphology of shahdad fan . Before creating shahdad south fault, this fan was very typical and big but after the south fault, changing contour line and cut this part. This revolutionize is one of the most important reason for us. So morphology of fan shows, filed study is one of the active tectonic regions (Fig 4 ,5 ).

(Fig 4) Before and after creating shahdad south fault

3- The series of faults having the direction of “North–western to South-Eastern and Northern and Southern" in drainage basin. Derakt – Tangan River is on the “North–

western to South-Eastern fault and cut the drainage basin, so this alluvial fan is formed in the effect of different materials erosion in to the drainage basin and laying these materials in the final called Loot. (Fig 5)

(Fig 5) show main faults

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III. SUMMARY AND CONCLUSION

According to the investigation on the effective factor in field study we found some evidence that are recognizing the area to tectonic. Geomorphic indicator is very important for recognizing active - tectonic place because identifying these regions helps us to understand rate and scale of movement. Therefore Studies of alluvial fans have some point, so investigator can get good information about relative age (rejuvenescence, growing up or youth, old). So there is one of the form that is very sensitive and tectonic and has a important - effective role on it . While Calculating active tectonic formula shows that, this region is very young, and this movement will be continuous. Now, we can see active tectonic that make a good role to uplift a creating shahdad south fault and this fault left a deep impression on the form of the fan.

REFERENCES [1] Al-Sarawi, M., 1988, Morphology and features of alluvial fans in

Kadhmah Bay, Kuwait: Journal of Sedimentary Petrology, v. 58, p. 902-907.

[2] Arzani , N .2005.The fluvial mega fan of Abarkoh Basin(Central Iran) an Example of flash- flood sedimentation in arid lands: Geological Society of Landon: Alluvial.

[3] Bull, W.B., 1964, alluvial fans and near-surface subsidence in western Fresno County, California: U.S. Geological Survey Professional Paper 437-A, 70 p.

[4] Beaty, C.B., 1974, Debris flow, alluvial fans and a revitalized catastrophism: Zeitschrift fur Geomorphologie, Supplement, v. 21, p. 39-51.

[5] Catto, N.R., 1993, Morphology and development of an alluvial fan in a permafrost region, Aklavik Range, Canada: Geografiska Annaler, v. 74A, p. 83-92.

[6] Clarke, A.O., 1989, Neotectonics and stream piracy on the Lytle Creek Alluvial Fan, Southern California: California Geographer, v. 29, p. 21-42.

[7] FEMA (Federal Emergency Management Agency)., 1996. Alluvial fan flooding: Nat'l Academy press, p:1-4.

[8] Gerson, R., Grossman, S., Amit, R., Greenbaum, N., 1993, Indicators of faulting events and periods of quiescence in desert alluvial fans: Earth Surface Processes and Landforms, v. 18, p. 181-202.

[9] Keller,E.A.,Pinter,N.1996.Activetectonics: Earthquakes,Uplift. And Landscape.Prentic Hall,Pub, p:301,122-146.

[10] Talegane .M , “Geomorphology of Iran”, Pub Gomess , 2002, P: 306 [11] White, K., Bryant, R., and Drake, N., 1998, Techniques for measuring

rock weathering: Application to a dated fan segment sequence in southern Tunisia: Earth Surface Processes and Landforms, v. 23, p. 1031-1043.

[12] Whipple, K.X., and Dunne, T., 1992, The influence of debris flow rheology on fan morphology, Owens Valley, California: Geological Society of America Bulletin, v. 104, p. 887-900.

[13] Wells, S.G., 1977, Geomorphic controls of alluvial fan deposition in the Sonoran Desert, Southwestern Arizona, in Doehring, D.O., ed., Geomorphology in Arid Regions, Eighth Annual Geomorphology Symposium, SUNY Binghamton, p. 27-50.

[14] Zomorodian .G, “Geomorphology of Iran”. Climatic and external dynamic processes, Ferdosi University of Mashad, 2002.

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