Interpretation of values variations of the Stream Length-Gradient Index (SL) in the north of the Syrian coastal mountain range - Kfariyah and Al-Qadisiyah sub-basins as a model

Abstract

Stream length gradient index (SL) is widely used in geomorphological studies aimed of detecting and interpreting knickzones along streams and their interpretation within the framework of the geological and morphological evolution of the area. The values of longitudinal gradient were calculated in the Kfariyah and Al-Qadisiyah sub-basins, in the north of the Syrian coastal range, where its values showed wide variance, explained according to geological and structural development of this range. These explanations, supported by field work data, allowed the development of a scenario about evolution of these streams. Initial stage of forming streams in the region is during Messinian when Mediterranean regress and a broad flat surface was formed, in parallel with the process of starting the rise of the coastal range. This was followed by a rapid sea transgression at the base of the Pliocene, which left debris deposits that covered this flat surface and filled streams valleys of Messinian. Continuing uplift of the coastal range and retreat of the sea at the end of Pliocene contributed to reactivation of streams. High values of (SL) were explained by reactivation of streams and the formation of a number of faults at a later stage of streams formation.