Crustal structure and rift tectonics across the Cauvery–Palar basin, Eastern Continental Margin of India based on seismic and potential field modelling

Abstract

The Cauvery-Palar basin is a major peri-cratonic rift basin located along the Eastern Continental Margin of India (ECMI) that had formed during the rift-drift events associated with the breakup of eastern Gondwanaland (mainly India-Sri Lanka-East Antarctica). In the present study, we carry out an integrated analysis of the potential field data across the basin to understand the crustal structure and the associated rift tectonics. The composite-magnetic anomaly map of the basin clearly shows the onshore-tooffshore structural continuity, and presence of several high-low trends related to either intrusive rocks or the faults. The Curie depth estimated from the spectral analysis of offshore magnetic anomaly data gave rise to 23 km in the offshore Cauvery-Palar basin. The 2D gravity and magnetic crustal models indicate several crustal blocks separated by major structures or faults, and the rift-related volcanic intrusive rocks that characterize the basin. The crustal models further reveal that the crust below southeast Indian shield margin is ∼36 km thick and thins down to as much as 13-16 km in the Ocean Continent Transition (OCT) region and increases to around 19-21 km towards deep oceanic areas of the basin. The faulted Moho geometry with maximum stretching in the Cauvery basin indicates shearing or low angle rifting at the time of breakup between India-Sri Lanka and the East Antarctica. However, the additional stretching observed in the Cauvery basin region could be ascribed to the subsequent rifting of Sri Lanka from India. The abnormal thinning of crust at the OCT is interpreted as the probable zone of emplaced Proto-Oceanic Crust (POC) rocks during the breakup. The derived crustal structure along with other geophysical data further reiterates sheared nature of the southern part of the ECMI.

Structure and tectonics of the continental margins of India and the adjacent deep ocean basins: current status of knowledge and some unresolved problems

“…This basin consists of block-faulted basement comprising of horst-graben architecture oblique to the coast, giving rise to several sub-basins separated by NE-SW trending subsurface basement ridges (Sastri et al, 1981). These sub-basins include the Ariyalur-Pondicherry, Tanjavur-Tranquebar, Nagapattinam and Palk Bay Sub-basins, separated respectively by the Kumbhakonam-Madanam, Karaikkal and the Vedaranyam ridges (Sastri et al, 1981;Twinkle et al, 2016;DGH, 2018a). Subsurface mapping carried out in the Cauvery Basin indicate that the Vedaranyam-Tiruchirapalli and the Madurai-Rameswaram trends cut across the general NE-SW trending horstgraben structures of the Cauvery Basin (Twinkle et al, 2016).…”

“…These sub-basins include the Ariyalur-Pondicherry, Tanjavur-Tranquebar, Nagapattinam and Palk Bay Sub-basins, separated respectively by the Kumbhakonam-Madanam, Karaikkal and the Vedaranyam ridges (Sastri et al, 1981;Twinkle et al, 2016;DGH, 2018a). Subsurface mapping carried out in the Cauvery Basin indicate that the Vedaranyam-Tiruchirapalli and the Madurai-Rameswaram trends cut across the general NE-SW trending horstgraben structures of the Cauvery Basin (Twinkle et al, 2016). Consequently, the Cauvery Basin is considered to have undergone three major episodes of tectonism that governed the development of basement structures consisting of three major N-S, NE-SW and NW-SE trending faults during three different phases (Mazumder et al, 2019).…”

Northeast monsoon variations during the Holocene inferred from palaeochannels and active channels of the Palar River basin, Southern Peninsular India

“…The Palar River basin is one of the major peri-cratonic rift basins situated along the east coast of India that has developed because of the rift-drift events linked with the breakup of India from the East Antarctica. Nayudupetta high detaches the Palar River from the adjacent Pennar basin in the north, and the Sri Lanka massif limits the basin in the south (Twinkle et al, 2016). The source area of the Palar River consists mainly of migmatites and granite.…”

Post-drill geophysical characterization of two deep-water wells of Cauvery Basin, East Coast of India

“…This rifting phase resulted in the formation of NE striking series of horst-graben structures (Fig. 1), which is indicative of extension and crustal stretching (Narasimha Chari et al 1995;Chand and Subrahmanyam 2001;Twinkle et al 2016;Qin et al 2017). These parallel trending subsurface highs are separating depressions from one another and extend into the offshore area (Fig.…”