Evaluation of relative active tectonics by using geomorphic indices of the Bamo anticline, Zagros Fold-Thrust Belt, Kurdistan Region of Iraq

Abstract

The Mountain Front Flexure forms a prominent morphotectonic structures along the Zagros Fold-Thrust Belt (ZFTB). It consists of several segments that defines tectonic salients and recessions within the belt. These segments are separated by strike-slip faults, including Khanaqin fault, which forms the boundary between the Kirkuk embayment and Lurestan Arc. The Bamo anticline is a complex N–S trending structure located above the Khanaqin fault zone, and it is thought to manifest active deformation in the Zagros Fold-Thrust Belt and along the fault. This study examines the state of active tectonics along the Bamo anticline through quantitative analyses of the evolved landscape using geomorphic indices. For that reason, six indices have been chosen for the analysis, such as stream length-gradient index (SL), drainage basin asymmetry (AF), hypsometric integral and hypsometric curve (HI & HC), ratio of valley-floor width to valley height (VF), basin shape (BS), and mountain front sinuosity (Smf). Each index's results were categorized into three classes, and the results from the first five indices, excluding Smf, were integrated to get the index of relative active tectonics (IRAT). This index was then compared with the results of Smf to assess the relative active tectonics (RAT) along the anticline. The results of the IRAT, classified into four classes from very high to low tectonic activity, reveal that no area is classified as class 1 (very high activity). However, 38% and 56% of the region are categorized as classes 2 (high activity) and 3 (moderate activity), respectively. Furthermore, the remaining 6% of the research area exhibits class 4 (low activity). The Smf values for the Northern, Middle, and Southern segments of the anticline are 1.12, 1.18, and 1.27, respectively. Consequently, based on the Smf data, all mountain fronts are classified as class 2 (moderate tectonic activity.