Journal of Spatial Analysis

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 Karst Geomorphology effects on the environmental hazard intrinsic vulnerability of groundwater resources (Case study: the Aleshtar and Nourabad basins)
 
Introduction
Karst is the result of the dissolution (physical and chemical) in carbonate (limestone and dolomite) and evaporate rocks. Karst developing is affected by climatological and geological factors. In the other words Karst landscapes and karst aquifers are formed by the dissolution of carbonate rocks by water rich in carbon dioxide waters. Karst aquifers include valuable freshwater resources, but are sometimes difficult to exploit and are almost always vulnerable to contamination, due to their specific hydrogeologic properties, therefore, karst aquifers require increased protection and application of specific hydrogeologic methods for their investigation. The groundwater protection in karst aquifer has a special importance, because the transit time for unsaturated and saturated zone is so quickly that the attenuation of the pollutant. Karst groundwater vulnerability mapping should form the basis for protection zoning and land use planning. A conceptual framework was devised for vulnerability mapping based on this European approach.
Social and economic life of cities such as Nourabad, Alashtar, and numerous rural societies is connected to the Gareen anticline springs. In this paper we used PaPRIKa method for vulnerability assessment in the Aleshtar and Nourabad basins.
 
Material and Methods
 The Gareen anticline in the Zagros Mountain range is located in the active deforming Zagros fold-thrust belt and Sanandaj-Sirjan zon. Alashtar and Nourabad karst aquifers are located in the north of Lorestan province. There are several thrust faults with northwest–southeast strike such as Gareen-Gamasiab and Gareen-Kahman Faults. Nourabad unit is composed mainly by gray limestone rocks, embedded marl limestone, recrystallized limestone and pyroclastic rocks. One of the most important features of the structural geology of the Alashtar unit, is abundance of the sedimentary rocks and scarcity of igneous rocks in this area. In other words In the Study basins the main geological formations incloud: Bakhtiarian conglomerate, carbonates of Sormeh, Taleh Zang, Pabdeh and Kashkan Formations.
The groundwater vulnerability assessment methods (PaPRIKa) applied at the test sites were designed specifically for karst aquifers. They are based on various types of information concerning the physical characteristics of the unsaturated and saturated zones, the aquifer structure and its hydrological behavior.
The PaPRIKa method takes into consideration criteria for both structure and functioning of the aquifer. Based on EPIK and RISK resource methods, PaPRIKa method was developed as a resource and source vulnerability mapping method, allowing assessing vulnerability with four criteria: Protection, Rock type, Infiltration and Karstification. The P map (Protection) considers the protection provided to the aquifers by layers above the aquifers: the S (soil texture, structure and thickness), Ca (permeability formations), the Uz (thickness, lithology and fracture degree of unsaturated zone) and E (Epikarst aquifer). Moreover, including the catchments of water losses where the vulnerability is higher. R map (Rock type) considers the lithology and the degree of fracturing of the sutured zone. I map (Infiltration) distinguishes concentrated from diffuse infiltration. Ka map (Karstification development) assesses the drainage capacity and the organization of the karst conduits network.
To  calculate  the vulnerability  index,  the  four  mentioned  maps(P. R. I. Ka)  have been  combined  using  the  following  equation coefficients (eq.1):
 
PaPRIKa Index= 0.2 P + 0.2 R + 0.4 I + 0.2 Ka                                        (1) eq
 
Due to the fact that karst geomorphology has a great impact on the quantitative and qualitative characteristics of water resources and the vulnerability assessment of these resources, fuzzy logic has been used to zonation of the Karst development in the Aleshtar and Nourabad basins.  In the fuzzy method used a gamma operator (eq.2):
µ _Combination= ((Fuzzy Algebraic Sum) (Fuzzy Algebraic Product)) ^1-γ                                                (2) eq                    
The vulnerability map for aquifers was prepared using the software Arc GIS_10.4.
 
Discussion and Results
In the Gareen Antarctic region, due to the availability of suitable Karstification, includes: Lithology, Active Tectonics, Mediterranean climate (with average rainfall of between 454-448 mm and average temperature of 13 C˚) features are formed by various forms of karst such as closed pits (Doline, Swallow Hole, Aven, Polyeh (Peljee), several types of Karrens, dissolution Cavities, small and large Caves and Springs. The most important karst features in this area including Dolines (Solutional, Collapse, Subsidence and Dropout) which are known the Karst Nival. Based on the Karst development zoning map by using the fuzzy logic, 15% of the study area has been developed. Due to the vulnerability based on PaPRIKa method, the Aleshtar and Nourabad basins divided into 5 categories. Resuls show that the vulnerability of the study area is mainly classified as High or Very High, due to the highly developed Epikarst, which minimizes the protective function of the unsaturated zone. There are many karst landforms such as dolines and Swallow Holes that are highly vulnerable.
 
Conclusions
The final evaluation of the vulnerability ground waters in the Aleshtar and Nourabad basins using the PaPRIKa method shows that the study area is divided into five vulnerable (very high, high, moderate, low and very low). So that areas with a very low, low and moderate vulnerability are 27.3%, 22.3% and 20.6% of the basin area respectively. Also that areas with a high and very high vulnerability are 17% and 12.8% of the study area cover, respectively. Due to the lack of soil and plant cover, heavy snowfall and the formation of Karst-Nival (including Dolines) highlands of the Gareen Anticline have a very high vulnerability potential. Validation of the results of the karstic aquifers vulnerability to Electrical Conductivity (EC) data and monthly discharge of springs shows that the Zaz and Ahangaran springs are in a high vulnerability zone. In the aquifer of this springs, Rapid reductions in EC are detected after each recharge period. Also in contrast Rapid increases in EC with reductions in recharge. This situation shows the High developed of this aquifers, as a result, the potential for vulnerability in these aquifers is high.
But in the springs of Niaz and Abdolhosseini in the Nourabad basin, the EC chart has not changed much compared to recharge. Therefore, the aquifer of these springs is less undeveloped or low developed and also less vulnerable.
 
Key Words: Gareen Anticline, Geomorphology, Karst, Lorestan, Pa
 
 

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 Investigation of morphometric indices of Assaluyeh, Varavi and Kangan anticlines in Fars Zagros and their relationship with tectonic activity
 
Extended Abstract
Introduction
Anticlines are the most prominent surface landforms whose geometry and morphology reflect mechanism of their formation and are keys to assessing the existence of deep faults that are effective in their formation and are among the most important seismic sources.
Detachment folds are formed by buckling of the rock units in response to shortening and are typically symmetric folds. Alternatively, asymmetric folds at the surface may be forced by the propagation of thrust faults at depth (fault propagation folds) or result from thrust movements along footwall ramps in the sedimentary pile (fault-ramp folds).The Zagros folds have often been interpreted as completely detached along the Hormuz salt.
Structurally, the study area is a part of the folded and coastal Zagros whose geological structure is simple and gentle and comprises a series of near-compact anticlines with a near-vertical axial surface and a northwest-southeast trend.
Outcrops of lithological formations in the study area include Surmeh, Fahliyan, Gadvan, Dariyan, Kazhdumi, Sarvak, Ilam, Gurpi, Pabdeh, Gachsaran, Mishan, Aghajari and Bakhtiari. In the northwestern part of the Kangan anticline, uplift of salt diapir along the Darang Fault has led to the exposure of limestone, shale, dolomite and anhydrite units of the Khami Group.
Assaluyeh is one of the most important economic bases in Iran and also one of the largest energy production areas in the world. With the rapid development of Assaluyeh region and increase of residential, urban and industrial constructions and refinery facilities, without attention to environmental hazards and especially earthquakes, it seems necessary to conduct this research.
The aim of this study was to investigate the morphometric characteristics of the Assaluyeh, Veravi and Kangan anticlines and its relationship with active tectonics in the region.
Methodology
At first, topographic, drainage network, slope, slope direction and tectonic maps of the anticlines were prepared using digital elevation model data, Landsat imagery and field surveys. Then, the geomorphic quantitative indices of the fold front sinuosity, aspect ratio, fold symmetry index, fold surface symmetry index, anticline crestline index, fold elevation index and spacing ratio were calculated. Qualitative studies were carried out on drainage pattern indices, triangular facets, wineglass valleys, linear valleys, fault scarps, springs, alluvial fans, etc. Finally, the relationship between all geomorphic and tectonic parameters was analyzed.
Results and discussion
Fold symmetry index is one of the most important parameters that show the degree of inequality of the two limbs of the anticline and thus the intensity of tectonic activity. In a completely symmetric anticline, the value of this index is 1, while in an asymmetric anticline the value of this index is less than 1. The index values for all three anticlines are less than one, but the Asalouyeh anticline shows more asymmetry, indicating a high tectonic activity on the anticline.
The fold front sinuosity index indicates the degree of tectonic activity or age of the folding system. The values obtained for this index in the three anticlines indicate that the anticlines are young and the tectonic forces are dominating the erosion.
The high value of the aspect ratios indicates the elliptical shape of the anticline, which is caused by the high stress perpendicular to the axis of the anticline. The index for Varai, Kangan, and Asalouyeh Anticlines are 0.7, 0.5 and 0.5, respectively, which again indicates nearly high tectonic activity in all three anticlines.
The spacing ratio index at the northern flank of Varavi and Assalouyeh anticlines and the southern flank of  Kagan anticline indicate a high value. Quantitative index of surface symmetry of folds also shows that all three anticlines are asymmetric and the asymmetry of Asalouyeh anticline is greater than Kangan and Varavi anticlines.
The drainage pattern is another indicator that, in the absence of tectonic evidence, can be a key to identifying tectonic activity.
The existence of asymmetric fork drainage networks is evidence of active tectonic evidence indicating lateral growth of anticlines. According to this criterion, Varavi anticline has grown to the northwest.
Comparison of the valleys shows that most of the valleys in Kagan anticline are of wineglass type whereas in Asalouyeh and Kangan anticlines linear valleys are more abundant. Some of these valleys are formed along transverse faults. The presence of numerous alluvial fans in the slopes of the Varavi anticline, indicates rapid erosion of the valley bed due to the rapid uplift and increasing valley slope. The presence of elongated and narrow V-shaped valleys is another evidence of the high tectonic activity of this anticline.
Conclusion
In seismicity studies and identification of hidden or blind fault studies, geophysical and geotechnical methods are expensive, time-consuming and require special equipment and are performed on a small scale. With the availability of landforms and features, risk assessment will be done at a lower cost, faster, and on a larger scale, if a relationship between landscapes and earthquakes can be established.
The geometry of the folds reflects the mechanism of their formation. Asymmetrical folds are associated with deep faulting and a detachment horizon, where the movement of sedimentary layers on the detachment horizon or at the tip of the hidden faults can cause an earthquake. The three anticlines of Assaluyeh, Varavi and Kangan are also part of the folded Zagros and have the characteristics of the folded Zagros.
In this study we defined a new index related to fold morphology, called fold surface symmetry index. Also we used fold morphology to detect the presence of detachment horizons and faults in the core of anticlines and their relationship to seismic hazard risk.
The results of this study show the transverse profile asymmetry of all three anticlines due to the association of these anticlines with the longitudinal faults in the anticline core and along their axes. The results of measurements of aspect ratios, fold front sinusitis, anticline ridge, and study of drainage patterns and tectonic landforms such as fault scarps, triangular facets, linear valleys also confirm the high tectonic activity of all three anticlines and the potential for earthquake hazard due to the movement of deep faults or any segments of them.