Tectono‐morphological evolution of the Cauvery, Vaigai, and Thamirabarani River basins: Implications on timing, stratigraphic markers, relative roles of intrinsic and extrinsic factors, and transience of Southern Indian landscape

Abstract

Peninsular India is an amalgam of transient landscapes evolved from the interactions between tectonic and climatic forcings. In order to appraise the tectono‐geomorphic evolution of South India, it is essential to understand the relationships between intrinsic and extrinsic processes and their geomorphic expressions at a river basin scale. Seven geomorphometric parameters, namely, longitudinal profile (Lp), asymmetry factor (Af), hypsometric curve and hypsometric integral (HI), mountain front sinuosity (Smf), river sinuosity (R), stream length gradient (Sl), and shape factor (Shp) were calculated for selected drainage basins of South India. Spatial analyses of these parameters in the light of systematic field mapping were attempted in this study. The results show the occurrences of southern sub‐basins with convex hypsometric curves indicating a youth stage and significant tectonic influence. The low and moderate Smf values within the basins are indicative of mountain fronts witnessing a high level of tectonic activity. The net effects of tectonic and geomorphometric processes are inferred to have been the responses of anti‐clockwise rotation of the Indian Plate and ridge uplift‐push from west. Directional change in Thamirabarani River Basin and drainage channel reorganizations in the Cauvery and Vaigai River basins stand testimony to these, among others. Amidst these, occurrences of tectonically quiescent regions and multiple incisions by river channels and flow of modern river channels in inherited palaeovalleys but on tangent directions of ancient flows are also observed. Five stages of landscape development are envisaged: First, inheritance of river basins from palaeodrainage systems; second, reversal of river flow directions during early part of Cenozoic and inception of evolution of modern river systems; third, during Miocene–Pliocene; fourth, during Pleistocene–Early Holocene; and fifth, during the Holocene–Anthropocene. The recent resurgence of tectonics is not only reflected in the shifting of axial rivers, but is also evidenced by seismicity and landslides/faulting. Together, transient nature of the Southern Indian Plate, first‐order control of tectonics, followed by climate and lithology over landscape evolution, inheritance of river valleys, synonymy of river basin responses to intrinsic and extrinsic geomorphic processes, however with unique signatures and basin‐scale responses, are inferred. Detailed morphometric studies and supplementation with precise age data may fine‐tune the proposed model. According to the model, inheritance of Mesozoic valley/structures during Late Jurassic–Early Cretaceous, drainage reversal and initiation of Cenozoic–Recent river basin evolution, intense peneplanation during Miocene–Pliocene, intense incision during Pleistocene, periodic climatic extremes during Early Cenozoic, Palaeocene–Eocene, Oligocene and corresponding pedogenesis, and terrace formation and sedimentation have been recognized. Based on the numerical ages and documentation of basin‐scale distribution of s...

Contrasting thermal histories for the Indian passive margins during syn‐ and post‐Gondwana break‐up: Insights from apatite fission‐track thermochronology

“…It is presently unclear whether this more recent pulse is a model artefact (e.g., Redfield, 2010) or related to exhumation. However, this cooling phase ties well with previous studies, advocating for reactivation and surface uplift during the Cenozoic (Lal et al, 2009; Ramkumar et al, 2016, 2019; Selvakumar and Ramasamy, 2014; Valdiya and Sanwal, 2017). There is a considerable post‐rift sedimentary influx into the Cauvery Basin (~4 km thickness; Richards et al, 2016) that can be related to Cenozoic thermal perturbations.…”

The Western Cameroon Highland margin: Is there any geomorphometric evidence of active tectonics?

“…Keller and Pinter (2002), Kirby and Whipple (2012), Mathew et al (2016), Menier et al (2017), Ramkumar, Menier, Mathew, Santosh, and Siddiqui (2017) and Ramkumar et al (2019) in several worldwide margins, Nsangou Ngapna et al (2018, 2019, 2020) and Balla Ateba et al (2021) in the South Cameroon margin within the West African passive margin evidenced tectonic activities on their landscape using geomorphometric indices. The critical evaluation of the WCHM geomorphological setting shows it is an uneven geomorphic unit developed on Palaeo‐ and Neoproterozoic basement and the Cretaceous to Recent volcano‐sedimentary cover and dissected by regional active tectonic structures such as the CCSZ, BTJ, MNSZ, TBF, Foumban‐Bankim Shear Zone (FSZ), SF, and the CVL.…”

Major, trace and rare earth elemental geochemistry of Santonian–Campanian onland‐offshore transition in a Gilbert‐type deltaic setting, Cauvery Basin, southern India

“…The Cauvery Basin is located in the southernmost part of Peninsular India (Figure 1). According to Powell, Roots, and Veevers (1988), it originated as a rift basin during the Late Jurassic–Early Cretaceous with a NE–SW trend and continued to evolve until the end of the Tertiary through the rift and associated structural movements (Chari et al, 1995; Powell et al, 1988) that were inferred to be a continuum of structural inheritance similar to other basins of the east coast of India (Ramkumar et al, 2017; Ramkumar et al, 2019; Ramkumar, Menier, Manoj, & Santosh, 2016). This basin consists of a number of sub‐basins, differentiated by structural highs (Kumar, 1983; Sastri, Raju, Sinha, Venkatachala, & Banerjee, 1977).…”