Lithostratigraphic development and neotectonic significance of the Quaternary sediments along the Kachchh Mainland Fault (KMF) zone, western India

Abstract

The Kachchh Mainland Fault (KMF) is a major E-W trending seismically active fault of the Kachchh palaeorift basin whose neotectonic evolution is not known. The present study deals with the eastern part of the KMF zone where the fault is morphologically expressed as steep north facing scarps and is divisible into five morphotectonic segments. The Quaternary sediments occurring in a narrow zone between the E-W trending KMF scarps and the flat Banni plain to the north are documented. The sediments show considerable heterogeneity vertically as well as laterally along the KMF zone. (The Quaternary sediments for a northward sloping and are exposed along the north flowing streams which also show rapid decrease in the depth of incision in the same direction.) The deposits, in general, comprise coarse as well as finer gravelly deposits, sands and aeolian and fluvial miliolites. The Quaternary sediments of the KMF zone show three major aggradation phases. The oldest phase includes the colluvio-fluvial sediments occurring below the miliolites. These deposits are strikingly coarse grained and show poor sorting and large angular clasts of Mesozoic rocks. The sedimentary characteristics indicate deposition, dominantly by debris flows and sediment gravity flows, as small coalescing alluvial fans in front of the scarps. These deposits suggest pre-miliolite neotectonic activity along the KMF. The second aggradation phase comprises aeolian miliolites and fluvially reworked miliolites that have been previously dated from middle to late Pleistocene. The youngest phase is the post-miliolite phase that includes all deposits younger than miliolite. These are represented by comparatively finer sandy gravels, gravelly sands and sand. The sediment characteristics suggest deposition in shallow braided stream channels under reduced level of neotectonic activity along the KMF during post-miliolite time evidenced by vertical dips of miliolites and tilting of gravels near the scarps. The tectonically controlled incision and dissection of the Quaternary deposits is the result of neotectonic activity that continues at present day. The overall nature, sedimentary characteristics and geomorphic setting of the sediments suggest that the KMF remained neotectonically active throughout the Quaternary period.

Transient Electromagnetic Investigations in a Tectonic Domain of the Kachchh Intraplate Region, Western India: A Morphotectonic Study of the Kachchh Mainland Fault

“…The eastern part of the NHR is represented by individual lobate‐shaped (elliptical anticlines in plan with curved limbs) anticlines in an en echelon pattern (Mallik et al, ). The primary KMF fault line at some places is buried under the Quaternary colluvio‐fluvial sediments (Chowksey et al, ) toward north of the NHR. The western part of the fault zone comprises subparallel converging or diverging faults between the Mesozoic/Eocene, Eocene/Miocene, and the Miocene/Pliocene formations.…”

“…In spite of many regional geophysical studies, shallow geophysical surveys done in the region are very limited (Mithila & Bansal, ), except a few site‐specific ground‐penetrating radar studies (Chowksey et al, ; Maurya et al, , ). Using the ground‐penetrating radar and coupled with field investigations, many active fault traces were identified in the region that suggested imprints of Holocene to post‐Tertiary tectonic activity along the faults (Kothyari et al, ; Mathew et al, ; Maurya et al, ; Patidar et al, , ; Prizomwala et al, ; Rajendran et al, ).…”

“…Using the ground‐penetrating radar and coupled with field investigations, many active fault traces were identified in the region that suggested imprints of Holocene to post‐Tertiary tectonic activity along the faults (Kothyari et al, ; Mathew et al, ; Maurya et al, ; Patidar et al, , ; Prizomwala et al, ; Rajendran et al, ). Chowksey et al () have suggested that the KMF is morphologically expressed as E‐W trending steep scarps, while the actual fault line is located further north and is buried under the Quaternary colluvio‐fluvial sediments. The northward‐tilted apron of the colluvio‐fluvial deposits overlapping the fault zone and incised fluvial valleys suggests the neotectonically active nature of the KMF (Chowksey et al, ).…”

“…Chowksey et al () have suggested that the KMF is morphologically expressed as E‐W trending steep scarps, while the actual fault line is located further north and is buried under the Quaternary colluvio‐fluvial sediments. The northward‐tilted apron of the colluvio‐fluvial deposits overlapping the fault zone and incised fluvial valleys suggests the neotectonically active nature of the KMF (Chowksey et al, ). Recent active electromagnetic imaging studies in eastern part of the Kachchh region infer anomalous behavior of the aquifer in the Katrol Hill Fault and the SWF zones, and a cumulative vertical throw of ∼60–65 m and 50–55 m for the SWF and the NWF blocks (Pavan Kumar et al, ) is estimated.…”

Shallow subsurface imaging of the Wagad active fault system (Kachchh, northwestern India) by time domain electromagnetic studies

“…The information on active faults and its subsurface geometry is essentially needed for effective seismic hazard assessment. Many active fault traces were identified in the region based on field (both geophysical and geological) investigations and satellite photo interpretation, which suggested imprints of Holocene to post Tertiary tectonic activity along the faults (Malik et al 2001;Mathew et al 2006;Patidar et al 2007Patidar et al , 2008Maurya et al 2013;Rajendran et al 2008;Chowksey et al 2011;Bhattacharya et al 2013;Kothyari et al 2016). GPR studies by Patidar et al (2007) indicated reactivation of the Kathrol Hill Fault (KHF) under compressive stress and suggested southward directed tilting of the geomorphic features due to neotectonic movements along the KHF.…”