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Title: 40K-40Ar dating of the Main Deccan large igneous province: Further evidence of KTB age and short duration
Authors: Chenet A.-L.
Quidelleur X.
Fluteau F.
Courtillot V.
Bajpai S.
Published in: Earth and Planetary Science Letters
Abstract: Most mass extinctions coincide in time with outpourings of continental flood basalts (CFB). Some 20 years ago, it was shown [Courtillot, V., Besse, J., Vandamme, D., Montigny, R., Jaeger, J.-J., Cappetta, H., 1986. Deccan flood basalts at the Cretaceous/Tertiary boundary? Earth Planet. Sci. Lett. 80, 361-374; Courtillot, V., Feraud, G., Maluski, H., Vandamme, D., Moreau, M.G., Besse, J., 1988. Deccan flood basalts and the Cretaceous/Tertiary boundary. Nature 333, 843-846; Duncan, R.A., Pyle, D.G., 1988. Rapid eruption of the Deccan flood basalts at the Cretaceous/Tertiary boundary. Nature 333 841-843] that the age of the Deccan traps was close to the Cretaceous-Tertiary (KT) boundary and its duration under 1 Myr. We have undertaken a new geochronological study, using the (unconventional) 40K-40Ar Cassignol-Gillot technique which is particularly well suited to the potassium-poor Deccan lavas. The mean of 4 determinations from the topmost (Ambenali and Mahabaleshwar) Formations is 64.5 ± 0.6 Ma. They straddle the C29r/C29n reversal boundary for which they provide a new constraint. The mean age of 3 determinations from the oldest (Jawhar) Formation is 64.8 ± 0.6 Ma. The difference in age between top and bottom of a 3500 m composite section, probably comprising 80% of the total Deccan volume, is statistically insignificant, with the overall mean age being 64.7 ± 0.6 Ma (N = 7). Our results are consistent with the most recent 40Ar/39Ar determinations [Knight, K.B., Renne, P.R., Halkett, A., White, N., 2003. 40Ar/ 39Ar dating of the Rajahmundry Traps, eastern India and their relationship to the Deccan traps. Earth Planet. Sci. Lett. 208, 85-99; Knight, K.B., Renne, P.R., Baker, J., Waight, T., White, N., 2005. Reply to '40Ar/39Ar dating of the Rajahmundry Traps, Eastern India and their relationship to the Deccan Traps: Discussion' by A.K. Baksi. Earth Planet. Sci. Lett. 239, 374-382], confirming that there should be no systematic difference between the two methods when they are used in an optimal way. An earlier, smaller but significant, pulse of volcanism between 68 and 67 Ma, extending over at least 500 km in latitude in the northern part of the Deccan CFB has also been identified. After 2 to 3 Ma of quiescence, the second, major phase of volcanism occurred near 65 Ma, expanding over most of the area covered by the first pulse and another 500 km to the South, consistent with drift of India by 300 to 450 km at ? 150 mm/yr during the quiescence period. New paleontological data from the remote Rajahmundry section [Keller, G., Adatte, T., Gardin, S., Bartolini, A., Bajpai, S., Humler, E., in prep. The Cretaceous-Tertiary boundary in Deccan Traps of the Krishna-Godavari Basin of southeastern India. EPSL to be submitted] suggest that this second pulse can itself be divided into two major pulses, one starting in C29r and ending at the KT boundary, the second starting in the upper part of C29r and ending within C29n. © 2007 Elsevier B.V. All rights reserved.
Citation: Earth and Planetary Science Letters (2007), 263(43832): 1-15
Issue Date: 2007
Publisher: Elsevier B.V.
Keywords: Deccan traps
short duration
ISSN: 0012821X
Author Scopus IDs: 8536639600
Author Affiliations: Chenet, A.-L., Laboratoire de Paléomagnétisme, Institut de Physique du Globe de Paris, UMR 7154, 4 place Jussieu, 75252 Paris cedex 05, France
Quidelleur, X., Laboratoire de Géochronologie, UPS-IPG Paris, CNRS UMR8148, Bat. 504, 91405 Orsay, France
Fluteau, F., Laboratoire de Paléomagnétisme, Institut de Physique du Globe de Paris, UMR 7154, 4 place Jussieu, 75252 Paris cedex 05, France
Courtillot, V., Laboratoire de Paléomagnétisme, Institut de Physique du Globe de Paris, UMR 7154, 4 place Jussieu, 75252 Paris cedex 05, France
Bajpai, S., Department of Earth Sciences, Indian Institute of Technology, Roorkee, 247 667, India
Funding Details: We wish to warmly thank P.-Y. Gillot for unlimited welcome and assistance in the laboratory which he set up. Many thanks to T. Salvany, A. Samper, A. Hildenbrand and J.-C. Lefèvre for assistance during age data acquisition. We acknowledge the field assistance in India of H. Bouquerel, B. Bonnefoy, M. Widdowson and S. Khadri, and continued support from K.V. Subbarao. S. Bajpai acknowledges support from the Council of Scientific and Industrial Research (CSIR), Govt. of India. The first version of the paper benefited from comments by Gerta Keller and two anonymous referees. Funding was obtained through a CNRS-ECLIPSE program. This is IPGP contribution 2240 and LGMT contribution 65. Appendix A
Corresponding Author: Chenet, A.-L.; Laboratoire de Paléomagnétisme, Institut de Physique du Globe de Paris, UMR 7154, 4 place Jussieu, 75252 Paris cedex 05, France; email:
Appears in Collections:Journal Publications [ES]

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