The Relationship of fault springs with wind erosion in Daranjir playa- Bafgh (Yazd Province)

Extended Abstract

Introduction

The wind erosion and the resulted landforms are the dominant landscape in flat and deep plains of Iran dry areas (Yamani, 2015). The importance of wind erosion in the deserts differs due to great variances in wind power (Goudie, 2013). This type of erosion which is controlled by the erosivity power of wind and the erodibility of impacted surfaces (sharma, 2010), is dangerous for three reasons: 1, the nutritious elements of the soil are destroyed and as a result the soil loses its power for keeping a conservative vegetation layer (Thomas, 2011). The deposition of eroded sediments can bury vegetation and river channels, pollute food and water reserves and also negatively impact the growth of vegetation, soil fertility, and the dynamics of ecosystem (Larney, 1998y; Worster, 2004; McTainsh & Strong, 2007 ). The transportation of eroded sediments through powerful winds can bring damage to buildings and products and also trouble visibility in roads and airports (Thomas, 2011).

Materials and methods
In first step, the impacted area of fault spring in Daranjir playa are identified based on satellite images, Geology maps and field observations. In the next step, 100 milliliter of water was sampled for chemistry analysis from active spring across Bafgh – Poshte-badam fault (Kor spring). Thus, to determine the water table, chemistry analysis of the sediment and water samples across Bafgh – Poshte-badam fault, 4 points were selected for drilling and the locations of bores were determined by GPS. To this end, the sampling procedure across the fault was conducted by a hand auger with the length of 20 cm and diameter of 7.5 cm. In sum, four water samples and 22 sediment samples were collected. In the geomorphology laboratory, initially the amounts of TDS, EC, and pH in the sample waters were measured by a multi parameter device, version HI9811-5. To measure the amounts of TDS, EC and pH in sand samples, saturated paste method was utilized. Here, the samples were initially dried in a drying device, and then 50 grams of each sample was measured with an accurate scale and mixed with 50 millimeters of distilled water. In the following step, the distilled water was mixed with sediment samples and the amounts of EC and TDS was measured using the multi parameter device and other devices.

Discussion and Results
The results suggest that the active tectonic performance across Bafgh-Posht badam fault not only result in the emergence of springs across the fault but also lead to the reduction of groundwater and the creation of a wet zone across the fault in Daranjir playa due to the penetration of water to the aquifer. This wet zone across the studied fault caused a significant growth of shrubs and Tamarix mascatensis, and reduced the speed of wind in the examined area. Regarding this Pye & Tsoar and state that in desert areas the salinity degree of groundwater has an important role in the transformation and distribution of deserts’ vegetation. The analyses of the qualitative and quantitative characteristics of groundwater across Bafgh- Posht badam fault show that the minimum water table, TDS and EC across the fault are ,respectively. In fact, by injecting fresh water across the fault, the fault springs not only reduce the salinity of groundwater but also raise the the water table across the mentioned fault and bring the transportation of the sediments to a minimum level. As for this case, Silva et al., (2018) state that in areas with high water tables, the sand sources are limited and consequently the transportation of sediments reduces. Moreover, Kocurek & Nielson concluded that high water tables can reduce the transportable sediment by conserving surface moisture. In addition to the formation of vegetation, the increase of water level across the fault, the creation and change of Nebkha formation location are the main effects of spring faults which have a crucial role in controlling wind sediments. As a matter of fact, the fresh water of springs results in the formation of vegetation and this vegetation captures wind sediments and forms Nebkhas.
Conclusion
The results of this study show the strike-slip movement of Bafgh – Poshte-badam fault and the emergence of fault springs have a key role in controlling wind erosion and formation of eaolian landforms in Dar-Anjir playa. Indeed, the fault springs control the wind erosion in the present case study in three ways: 1: the formation of wet zone creates various types of vegetation and reduces wind speed in surface, 2: the raising of water table across Bafgh – Poshte-badam fault and the increase of the moisture surface impede the movement of sediment by wind and 3: With formation of nebkhas causes the aeoilan sediment accumulation around Shrubs.