Did Deccan volcanism pre-date the Cretaceous/Tertiary transition?

Abstract

Nine basalt samples collected from the bottom to the top of a > 2.5 km thick composite section in the western margin of the Deccan Flood basalt province, India, yield⁴⁰Ar-³⁹Ar plateau ages between 67 and 62.5 Ma relative to an age of 520.4 Ma for the monitor standard MMhb-1. These ages are consistent with the stratigraphy and comparable to earlier results [1]. They indicate that the lower ~2 km thick reversely magnetised lava sequence erupted within ~ Ma close to 67 Ma ago and the eruption interval even for the exposed and surviving units of the Deccan was not less than 3 Ma. With the Cretaceous/Tertiary boundary as demarcated by Haiti tektites (65.2 ± 0.1 Ma) [2] and melt rock glasses from Chicxulub crater dated precisely at 64.98 ± 0.10 Ma [3] relative to MMhb-1 (age 520.4 Ma), our results on the thick reversely magnetised lava units imply their eruption before the Cretaceous/Tertiary boundary events by more than the 1.0 Ma.