The Tectonic “Umbilical Cord” Linking India and Sri Lanka and the Tale of their Failed Rift

Abstract

Geophysical studies of the tectonic links between Sri Lanka and India are limited, and consequent paleo‐fit configurations differ and remain uncertain. Here, we present first‐order constraints for an optimum link between Sri Lanka and southern India by using high‐resolution maps of elastic thickness (Te) and crustal thickness (Tc) derived from a flexure inversion method that based on the space‐domain convolution technique for a data window covering integral continental‐oceanic lithospheric setting. We find that the spatial variations of Te and Tc over different crustal provinces in southern India and Sri Lanka agree well with their tectonic classifications proposed by geological studies. Importantly, this study provides much‐needed confirmation of the rifting and associated lithospheric deformation along the mirrored continental margins of India and Sri Lanka and in the intervening transitional lithosphere. The two margins are marked by patterns of low Te and thinned crust, which suggests that an anticlockwise rift (eastward rift) of Sri Lanka away from India resulted in the creation of the Mannar Basin, and a secondary N‐S rifting gave rise to the Cauvery Basin. However, these developments led to a final failed rift, which we attribute to a mechanically strong continental lithospheric bond (a NW‐SE zone of high‐Te and relatively thick crust) that was present in the intervening Palk Strait. We matched the identical zones of Te variations along the two mirrored continental margins and thus obtained a coherent paleo‐fit configuration, and a step‐by‐step evolution of these margins was constructed by using magnetic anomaly‐based paleo‐fit reconstruction models.

Continental flood basalt magmatism contemporaneous with Deccan traps in the Mannar basin, offshore Sri Lanka

“…Although Sri Lanka is placed between East Gondwana and West Gondwana, its relative position with India, Madagascar, and Antarctica is variable (Dissanayake & Chandrajith, 1999;Katz, 1978;Köbben et al, 2016;Ratheesh-Kumar et al, 2020;Smith & Hallam, 1970;Yoshida et al, 1992;Yoshida et al, 2003) which depends on the tectonics associated with the Gondwana assembly. East Gondwana break up started at around 140 Ma (Gibbons et al, 2013).…”

“…Chemical composition, spatial and temporal occurrence of magmatic rocks in such basins help reconstruct associated tectonics and palaeogeographic reconstructions (Collier et al, 2008;Courtillot et al, 1999;Pande et al, 2001;Pandey et al, 2019;White & McKenzie, 1989). Mannar basin located between southern coast of India and western coast of Sri Lanka is a failed rift basin (Curray, 1984;Herath et al, 2017;Lal et al, 2009;Rana et al, 2008;Ratheesh-Kumar et al, 2020). Water in the northern part of the basin is shallow, while it reaches more than 3000 m towards the southern part (Baillie et al, 2002;Kularathne et al, 2015;Premarathne et al, 2015).…”

Modeling of the Petroleum System in the Cauvery Basin, Sri Lanka

“…Many researchers (e.g. Chandra et al, 1991;Chari et al, 1995;Baillie et al, 2003;Premarathne, 2008;Rana et al, 2008;Rao et al, 2010) consider the Mannar basin to be the southern extension of the Cauvery Basin. The petroleum geology of the Sri Lankan sector of the basin has been addressed by Cantwell et al (1978) and Premarathne (2015Premarathne ( , 2020.…”

“…1), have been formed during the seafloor spreading between India and Antarctica in the early Cretaceous (Lal et al, 2009). Stratigraphy, tectonic setting, and hydrocarbon prospectivity of the Indian side of the Cauvery Basin have been addressed in detail by Sastri et al (1973;1981); Chandra et al (1991); Ramana et al (1995); Murthy et al (2008); Rana et al (2008); Lal et al (2009); Rao, et al (2010); Chaudhuri et al (2010); Chakraborty et al (2018); Bastia and Radhakrishna, (2012), etc. Those facts on the Sri Lankan counterpart have been addressed by Cantwell et al, (1978); Premarathne, (2008Premarathne, ( , 2015Premarathne, ( , 2017Premarathne, ( , 2020; Bandara et al, 2020).…”

Hybrid phase equilibria modelling with conventional and trace element thermobarometry to assess the P–T evolution of UHT granulites: An example from the Highland Complex, Sri Lanka

“…The rocks in these three complexes were metamorphosed under upper amphibolite to granulite facies conditions simultaneous with the assembly of Gondwana (e.g. Cooray, 1994; He et al., 2015, 2016; Hirayama et al., 2020 Kehelpannala, 1997; Kröner et al., 2013; Malaviarachchi et al., 2019; Mathavan et al., 1999; Perera & Kagami, 2011; Ratheesh‐Kumar, Dharmapriya, Windley, Xiao, & Jeevan, 2020).…”