| Abstrakt: |
Integrated morphometric, morphostructural and geomorphological analyses are used to unravel the modifications that affected the Chaliyar river basin particularly due to active tectonics. Morphostructural analysis has given qualitative evaluation of the relation between tectonic structures and drainage network geometry. The association between the drainage directions of various stream orders with lineaments was evaluated by comparing the rose diagrams of drainage directions and trend of the lineaments. Geomorphic anomalies that are detected and characterised in the Chaliyar river basin have given supplementary tool to understand the subtle tectonic movements in the region. It is affirmed that these morphological manifestations identified in this terrain are the result of active strike–slip faulting. The deflected and beheaded streams, shutter ridges, river ponding, faults scarps, small horst and graben, compressed meander and landslides suggest tectonic creep occurred in the past few thousand years. It is assumed that two tectonic phases existed in the studied area. The first, a compressive phase responsible for the development of folded structures, over thrust, reverse faults and strike–slip faults and occurred on a regional scale. The second, a neotectonic phase connected with general uplift produced normal faults which displaced the geological structures, formed during the compressive tectonic phase. This neotectonic activity has displaced the fluvial terraces and is responsible for the sharp channel deviation within the basin. Block fault sequel with the evolution of Western Ghat escarpment with subsequent reactivation along the lineaments and circum-denudation of the faulted blocks resulted in the evolution of the Nilambur valley. Stream channels were morphologically adjusted over a short period of time and as the basin is located in a tectonically active region from the time of development of Western Ghat escarpment have played a dominant role in changing the morphology of the Chaliyar river basin. [ABSTRACT FROM AUTHOR] |
