Quaternary Landform Development in the Central segment of tectonically active Kachchh Mainland Fault zone, Western India

Abstract

The landform aggradation in an arid climatic region is often regulated by external forces, that provide signatures of climate and tectonic perturbations. The landforms in the central segment of Northern Hill Range (NHR), which marks the surface expression of Kachchh Mainland Fault (KMF), are investigated in this study to understand the role of climatic changes and tectonic activity during the time of aggradation and incision. Geomorphologically, the KMF is expressed by the presence of ∼80–150 m high E-W trending escarpment. The central segment of KMF preserves the alluvial fan surfaces which have been truncated at several places with anomalous incision. Conventional morphometric analyses indicate that the KMF is affected by tectonic activity in recent times. The optical chronology of oldest alluvial fan dated from back limb and forelimb of an anticline was around 28 ka (with gradual onset of aridity) and 25 ka (with peak aridity). This arid phase is correlated with enhanced tectonic uplift along the KMF, which is manifested in the form of strath terraces and incision of river valleys. The oldest activity pre-dated to 25 ka and continued till 14 ka and there was a tectonic stability between 14 and 8 ka. The younger activity began soon after 8 ka and continuous till today, which is most likely caused by the manifestation of the Early Holocene climatic optima that lead to severe erosional processes. The younger Middle Holocene (4.3 ka) event is correlated with enhanced uplift and was accountable for the down cutting of the fill sediments and the Mesozoic bedrock. The study suggests that the deformation pattern close to KMF is the result of localized compressive stress generated between two fault segments.

Keywords

• Kachchh mainland fault (KMF)
• Optical dating
• Geomorphic indices
• Active deformation
• Kachchh