Deccan volcanism at the Cretaceous/Tertiary boundary; Data and inferences
V. Courtillot, D. Vandamme, J. Besse, J. J. Jaeger, M. Javoy, 1990. "Deccan volcanism at the Cretaceous/Tertiary boundary; Data and inferences", Global Catastrophes in Earth History; An Interdisciplinary Conference on Impacts, Volcanism, and Mass Mortality, Virgil L. Sharpton, Peter D. Ward
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The proposal that the Deccan flood basalts erupted during a period of 500,000 years, at most—rather precisely at the Cretaceous/Tertiary (K/T) boundary—is based on paleomagnetic, paleontological, and geochronological data, which are briefly reviewed. Geochemical anomalies with a complex time signature are found in many K/T boundary sedimentary sections and may reflect multiple volcanic events, with the major one occurring in possibly some 10,000 years at K/T boundary time, for which an absolute age can be proposed from Deccan Ar ages (65.7 ± 2.0 Ma; N = 24 ages). The fact that short-term (<106 yr) K/T boundary anomalies in the sedimentary record often ride on longer term (>106 yr) anomalies is interpreted as being related to two different modes of convection in the mantle (“instability” versus “normal”), with a common primary cause. It is suggested that this cause lies in major ~170-m.y. fluctuations in thickness of the D″ layer, possibly with second-order fluctuations of 30-m.y. periodicity that still need to be confirmed.