Quantitative analysis of relative tectonic activity in the Jarahi-Hendijan basin area, Zagros, Iran

Abstract

Quantitative analysis is a major factor controlling landform development in tectonically active regions, and it has significantly affected fluvial systems and mountain-front landscapes in the Jarahi-Hendijan basin area of the Zagros, southwest Iran. The area is located along the high Zagros, Zagros simple folded belt and coastal plain. It is an outcome of the SE-NW oriented tectonic conversion that initiated in the Late Cretaceous and strengthened during the Early Miocene due to the collision of the Arabian and Eurasian plates. To assess tectonic activities in the area, we have analyzed geomorphic indices: the stream-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), valley floor width-valley height ratio (Vf), drainage basin shape (Bs) and mountain-front sinuosity (Smf). These indices were combined to yield the relative active tectonics index (Iat) using geographic information systems (GIS). Based on Iat values, the study area was divided into four parts: Class 1 (very high relative tectonic activity, 11.5% in area); Class 2 (high, 27.7%); Class 3 (moderate, 23.4%), and Class 4 (low, 37.4%). The results are consistent with field observations on landforms and the regions with high relative tectonic activity mostly correspond with the active mountain front faults at the northern part of study area. The coastal plain in the west and southwest of the area show the lowest relative tectonic activity (class 4).