Geomorphology and growth analysis of the Birjand blind thrust-related anticline by variations in the fractal dimension of drainage patterns

Abstract
The Birjand anticline is a type of the fault propagation fold that is formed above a blind thrust fault and is divided into 11 segments by 12 tear faults. In this research, the Late Cenozoic deformation associated with the Birjand blind thrust has been evaluated. To this end, the fractal dimension of drainage patterns and its statistical properties is calculated on the Birjand anticline. Accordingly, the spatial distribution of windows with the fractal dimensions close to 2 are within the regions that are low slope, low height and marl-tuff units. These windows are more relative frequency in the northern limb of the fold, also to the northwest end segments (10 and 11). This issue is related to a gentle back-limb of the fold and flat crest of the end segment 11. For Birjand anticline toward northwest, lateral growth of the fold is clearly at the Dasht-e Birjand and close to the Shekarab kuh to form as gently-dipping alluvial fans deposited. In the progressive stages of the Birjand anticline growth, segments from northwest to the southeast have grown more structurally mature and the values of the fractal dimension are lower. In the back-limb and flat crest of the fold, the drainage patterns are closer to trellis and dendritic and the fractal dimension approaches to 2 and in the fore limb are intermediate and steep slope, the drainage patterns are varies to parallel and the fractal dimension is decreasing. The surface deformation due to the Birjand blind thrust geometry controls the pattern and density of the drainage network by effects of topography and lithology and the result is a high the fractal dimension in the region with more active tectonic.