The Cauvery Basin, formed as a result of the fragmentation of Gondwana during the Late Jurassic/Early Cretaceous period, is located on the eastern continental margin of India. The basin, covered under thick Phanerozoic sediments, has a geochronological lesser understood basement that forms the easternmost extremity of the Madurai Block in the Southern Granulite Terrane. This paper reports Rb–Sr and Sm–Nd ages between 2173–2307 Ma from northern onshore and Rb–Sr ages between 1223–983 Ma from southern offshore parts of the basin. The studied samples include basement core samples of hornblende–gneisses, granites, and metapelites (chlorite–biotite and garnet–biotite schists). These ages represent at least two episodes of tectonothermal events during Early Paleoproterozoic and Late Neoproterozoic, suggesting a polymetamorphic history of the basement and are correlatable with the reported events. The study also yielded Early Paleozoic Cambro–Ordovician whole-rock-biotite mineral Rb–Sr ages of 443–487 Ma, coinciding with the cooling stages of the Pan-African tectonothermal event post the thermal resetting in the studied basement of the Cauvery Basin. Further, the Sm–Nd systematics yielded two groups of model ages (2.1–3.4 Ga and 1.5 Ga), based on which two distinct crustal domains have been identified in the basement, viz., a Paleoarchean to Early Paleoproterozoic northern domain and an Early Mesoproterozoic southern domain, respectively. This has also been supported by distinct radiometric ages obtained fromthese domains.
Volume 132, 2023
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