SE5
Flood Basalts, Mantle Plumes, Continental Rifting and Mass Extinctions

Main Organiser
Kanchan Pande, Planetary and Geosciences Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380009, INDIA.
kanchan@prl.enet.in

Co-Organiser(s)
Prof. Sun-Lin Chung, Department of Geosciences.
sunlin@ccms.ntu.edu.tw

Brief Description
The observed association of several continental flood basalt provinces, mantle plumes, continental rifting and mass extinction events have led to models/hypotheses proposing correlations and genetic links amongst them. For example, the eruption of the Deccan flood basalt in India have been linked to the Cretaceous-Tertiary Boundary (KTB) events, the Reunion mantle plume and breakup of India and the opening of the Indian Ocean. Similarly, the Emeishan flood basalt in SW China have been linked to the Permian-Triassic Boundry (PTB) events, the rifting of Qiangtang Terrane of Tibet from the main South China block and a starting plume. These hypotheses, however, are still being debated and it is appropriate and timely that we review the status and outline the future course of our studies that could help in evaluating/ constraining these hypotheses. A few important questions that need to be addressed are: Temporal coincidence between mantle plumes, continental flood basalts and breakup have been observed for long but the initiating factor is still being debated. Was rifting triggered by doming above the thermal plume or was rifting the driving force? A possible answer will depend critically on determining the precise age and duration of these phenomena based on unambiguous chronological data and palaeomagnetic reconstructions. We need to assess these data from the various flood basalt provinces such as the Deccan, Emeishan and Rajmahal. The proposition of a pre-Deccan history for the Reunion hotspot based on the volcanic rocks of South Tethyan Suture Zone needs a serious consideration for its possible bearing on the plume-head model of flood basalt generation. The role of flood basalts in causing mass extinctions needs to be evaluated in the light of their synchrony, duration and the now available detailed fossil and stratigraphic records for both the Cretaceous-Tertiary and Permian-Triassic boundaries.