ACCELERATING DECCAN ERUPTIONS AND RUNAWAY CLIMATE CHANGE

Deccan Volcanic Province erupted ~80% of the total volume during C29r flooding the Indian continent with ~1.5 million km³ of lava that forms >3000 m high mountains. The base of C29r was recently dated (U-Pb) at ~66.250 Ma [1] and the Cretaceous-Paleogene boundary (KPB) at 66.043 Ma [2]. Volcanic eruptions released tens of thousands of gigatons of CO₂ and SO₂ that resulted in rapid global climate warming by 3-4 ºC in the oceans and 7-8 ºC on land and surface ocean acidification caused major environmental stress. Accelerating massive eruptions culminated in runaway effects during the last 10 ky of the Maastrichtian, including a second hyperthermal warming of 5-7 ºC in less than 2 ky, ocean acidification and rapid mass extinctions based on bio-, chemostratigraphy and sedimentation rates [3].

In SE India the mass extinction in planktic foraminifera is documented between the longest lava flows >1000 km from the main eruption center of the Western Ghats [4]. In Meghalaya, NE India, ~800 km from the Deccan volcanic province, more than 95% of the assemblage consists of high-stress morphotypes of the disaster opportunist Guembelitria cretacea, the only long-term global KTB survivor [5]. The mass extinction is extremely rapid worldwide and may appear instantaneous due to low sedimentation rates, non-deposition or erosion. But in areas of high sediment accumulation the last 30 ky of the Maastrichtian can be resolved. For example, at Elles in Tunisia, the average sediment accumulation rate for the 250 ky of C29R below the KPB is 8.6 cm/ky.

Recent speculations that the Chicxulub impact triggered the massive Deccan eruptions remain unsupported [6]. Although superficially Deccan runaway effects may suggest support for such a scenario, it may be impossible to prove. Biostratigraphic evidence from NE Mexico, Texas and the crater core Yaxcopoil-1 indicates the Chicxulub impact predates the KTB by about ~90-100 ky [7].

[1] Schoene et al., 2015, Science 347,182-184. [2] Renne et al., 2013, Science 339, 684-687. [3] Punekar et al., 2014, GSA S Paper 505, 91-116. [4] Keller et al., 2012, EPSL 341-344, 211-221. [5] Gertsch et al., 2011, EPSL 310, 272-285. [6] Richards et al., 2015, GSA Bull. doi:10.1130/B31167.1. [7] Keller et al., 2009, JGS London 166, 393-411.