Cenozoic epeirogeny of the Indian peninsula

Abstract

Peninsular India is a cratonic region with asymmetric relief manifest by eastward tilting from the 1.5 km high Western Ghats escarpment toward the floodplains of eastward‐draining rivers. Oceanic residual depth measurements on either side of India show that this west‐east asymmetry is broader scale, occurring over distances of > 2000 km. Admittance analysis of free‐air gravity and topography shows that the elastic thickness is 10 ± 3 km, suggesting that regional uplift is not solely caused by flexural loading. To investigate how Indian physiography is generated, we have jointly inverted 530 river profiles to determine rock uplift rate as a function of space and time. Key erosional parameters are calibrated using independent geologic constraints (e.g., emergent marine deposits, elevated paleosurfaces, uplifted lignite deposits). Our results suggest that regional tilt grew at rates of up to 0.1 mm a−1 between 25 Ma and the present day. Neogene uplift initiated in the south and propagated northward along the western margin. This calculated history is corroborated by low‐temperature thermochronologic observations, by sedimentary flux of clastic deposits into the Krishna‐Godavari delta, and by sequence stratigraphic architecture along adjacent rifted margins. Onset of regional uplift predates intensification of the Indian monsoon at 8 Ma, suggesting that rock uplift rather than climatic change is responsible for modern‐day relief. A positive correlation between residual depth measurements and shear wave velocities beneath the lithosphere suggests that regional uplift is generated and maintained by temperature anomalies of ±100 °C within a 200 ± 25 km thick asthenospheric channel.

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

“…On a regional perspective, the sprawl and number of sub‐basins found to be tectonically active according to the Smf values are on a decreasing trend from south toward north and provide affirmative evidence to the previous inference of diminutive tectonism from S–N as a result of reducing ridge push and uplift. These inferences also concur with the report of emergence of WGE that proceeded from south–north since Early Cenozoic and continual tilt toward east, intensively since 25 Ma (Richards et al ().…”

“…Although the reversal of drainage flow directions was initiated by the evolution of WGE (Fainstein et al, ) during early Cenozoic, significant denudation due to tectonics (to provide slope and continued emergence of provenance) with the active support by climate (to provide conducive milieu for weathering and pedogenesis) caused extensive basinfills during Miocene–Pliocene as indicated by extensive delta development all along the eastern continental margin of India (Singh & Swamy, ). Richards et al () reported significant tectonic tilt toward east since 25 Ma that continue until today. Ramkumar et al () stated that during the Neogene, inherited Gondwana structures were reactivated.…”

“…Singh and Rajamani () attested this inference and suggested the prevalence of this phenomenon on a regional basinal–continental scale. Richards et al () reported that, though the topographic rise of WGE commenced during Early Cenozoic, that proceeded from south to north, perhaps as a domineering result of uplift and ridge‐push from south (Ramkumar et al ), the ridge‐push from west contribute toward anticlockwise rotation and easterly tilt, which in turn was intensive since 25 Ma and continue until today at a rate of 0.1 mm/year. The common occurrences of physical erosion, the absence of chemical weathering, and episodic bouts of clastic sediment flux into the Cauvery Basin during Barremian, Santonian, and Mio‐Pliocene were reported by Ramkumar et al (, 2011 and 2013).…”

Neogene Uplift and Magmatism of Anatolia: Insights From Drainage Analysis and Basaltic Geochemistry

“…The minimum misfit between observed and calculated river profiles is obtained for a value of m 0:45. The locus of this minimum is not strongly dependent on the degree of spatial or temporal smoothing that is applied, contra Richards et al (2016). We aim to find values of the two damping parameters that yield the smoothest possible model which still adequately fits the observed river profiles.…”

Spatial and temporal uplift history of South America from calibrated drainage analysis

“…Subsequently, Roberts et al [2012a] developed a non-linear optimization scheme that permits substantial inventories of river profiles to be simultaneously inverted by varying uplift rate history as a function of both time and space. This general scheme has been successfully applied to different continents and suggests that the empirical stream-power formulation provides a practical basis by which patterns of regional uplift through space and time can be assessed [Roberts et al, 2012b;Czarnota et al, 2014;Paul et al, 2014;Wilson et al, 2014;Stephenson et al, 2014;Richards et al, 2016].…”