Timing and tempo of Deccan volcanism relative to the KTB extinction, what we can learn from the redboles ?

Deccan Traps erupted in three main phases with 6% total Deccan volume in phase-1 (C30n), 80% in phase-2 (C29r) and 14% in phase-3 (C29n). Recent studies indicate that the bulk (80%) of Deccan trap eruptions (phase-2) occurred... [ view full abstract ]

Deccan Traps erupted in three main phases with 6% total Deccan volume in phase-1 (C30n), 80% in phase-2 (C29r) and 14% in phase-3 (C29n). Recent studies indicate that the bulk (80%) of Deccan trap eruptions (phase-2) occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology shows that the main phase-2 began 250 ky before the Cretaceous-Tertiary (KT) mass extinction and continued into the early Danian suggesting a cause-and-effect relationship.
Closer to the eruption center, the lava flows are generally separated by red weathered horizons known as red boles that mark quiescent periods between basalt flows. Red boles have increasingly attracted the attention of researchers to understand the climatic and paleoenvironmental impact of Continental Flood Basalts (CFB). Recent advances in U-Pb dating of Deccan lava flows, studies of weathering patterns and paleoclimatic information gained from multiproxy analyses of red bole beds (e.g., lithology, mineralogy, geochemistry) yield crucial evidence of environmental changes triggered by volcanic activity. Red boles consist mainly of red silty clays characterized by concentrations of immobile elements such as Al and Fe3+ ions that are typical of paleo-laterites which probably developed during the short periods of weathering between eruptions. At least 30 thick red bole layers are present in C29r below the KT boundary between lava flows of phase-2 that erupted over a time span of about 250 ky. The short duration exposures of these red boles are reflected in the mineralogical and geochemical data that indicate rapid weathering (high CIA) linked to increasing acid rains. ∂D and ∂18O measured on smectite clays from the redboles approximate the meteoric water composition that prevailed during Deccan eruptions. Preliminary isotopic data from redboles deposited during the main phase-2 suggest significant and rapid changes in rainfall intensity and/or altitude linked to the accumulation of a 3100m thick basalt pile that erupted over a short period of time.