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40Ar/39Ar ages of alkaline and tholeiitic rocks from the northern Deccan Traps: implications for magmatic processes and the K–Pg boundary


Laura Parisio1, Fred Jourdan2, Andrea Marzoli1,3, Leone Melluso4, Sam F. Sethna5, Giuliano Bellieni1

1Dipartimento di Geoscienze, Università degli Studi di Padova, Via Gradenigo 6, 35131 Padova, Italy
2Western Australian Argon Isotope Facility, JdL Centre & Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
3CNR-IGG Padova, Via Gradenigo 6, 35131 Padova, Italy
4Dipartimento di Scienze della Terra, Ambiente e Risorse, Università di Napoli Federico II, Via Mezzocannone 8, 80134
Napoli, Italy
5Department of Geology, St. Xavier’s College, Mumbai, 400001, India
Journal of the Geological Society, London, 173, 679-688
The Deccan large igneous province in India was emplaced temporally close to the Cretaceous–Palaeogene (K–Pg) boundary and is formed by tholeiitic flood basalts and less abundant alkaline rocks. Definition of the origin of Deccan magmatism and of its environmental impact relies on precise and accurate geochronological analyses.We present new 40Ar/39Ar ages from the northern sector of the province. In this area, tholeiitic and alkaline rocks were contemporaneously emplaced at 66.60 ± 0.35 to 65.25 ± 0.29 Ma in the Phenai Mata area, whereas rocks from Rajpipla and Mount Pavagadh yielded ages ranging from 66.40 ± 2.80 to 64.90 ± 0.80 Ma. The indistinguishable ages for alkaline and tholeiitic magmatism suggest that distinct mantle sources were synchronously active. The new ages are compared with previous ages, which were carefully screened and filtered and then recalculated to be comparable. The entire dataset of geochronological data does not support a time-related migration of the magmatism related to the northward Indian plate movement relative to the Reunion mantle plume. The main phase of magmatism, including the newly dated rocks from the northern Deccan, occurred at the K–Pg boundary. This suggests a causal link between the emplacement of the province and the K–Pg mass extinction.