Reptilian vertebrates from Deccan volcanic associated sediments of Malwa Plateau in context to reptiles across Maastrichtian-Paleogene volcanic eruptions in Main Deccan Volcanic Province,India

The enormous eruptive volume of India's Deccan continental flood basalts has been linked to global mass extinction at Cretaceous-Paleogene boundary and destablilisation of both marine and terrestrial ecosystems before and after the Chicxulub bolide impact. Deccan Volcanic Province(DVP) currently covers around 500 000 km^2 of land between latitude 15°10′-24°30′N and longitude 70°10′-82°10′E over central India towards the west coast. The pre-erosional volume is estimated at around 1.6 million km^3 which is one of the largest volcanic eruptions on the Earth. The Deccan lava flows in geographically separated areas in DVP are considered to have separate sources and sites of eruptions and were outpoured in different magnetochrons viz. C30 n to C28 n of Maastrichtian to Paleocene. The Deccan volcanic sequences(DVS) in different provinces are associated with(i) sediments deposited before the arrival(Ground Zero) of the first lava flows-designated as infratrappean or Lameta sediments and(ii) sediments between the lava flows deposited during the period of quiescence at different stratigraphic levels designated as intertrappean(interflow) sediments. The Ground Zero Lameta sediments are the major dinosaur bearing sediments deposited in six inland basins viz. 1. Balasinor-Jhabua;2. Sagar;3. Jabalpur;4. Ambikapur-Amarkantak;5. Salburdi;6. Nand-Dongargaon. The sediments represent mainly the terrestrial ecosystems destabilised by the volcanism and they record history of biotic and environmental changes impacted by the volcanism across the Deccan volcanic eruptions. The titanosaurs, crocodylimorphs and bothremydid turtles survived across the first flows in the region in the C30 n. The skeletal remains of the surviving reptiles are preserved in the Deccan volcanic associated intertrappean lake sediments at different stratigraphic levels higher-up in the sequence. Locally, in the Malwa region the Scincomorp and Anguimorph lizards make their first appearance during the earlier phase of volcanic eruptions in C30 n wherein their well preserved bones are found in the intertrappean/inter lsva lake sediments deposited between the lava flows. The lizard fauna is indicated to have better flourished after the initial Deccan eruptions possibly owing to increased humidity.

Untangling the biotic stress in the late Maastrichtian Deccan-benchmark interval of Bidart(France)

The late Maastrichtian witnessed substantial surges in Deccan volcanism,prompting the hypothesis that these voluminous pulses may have instigated repeated episodes of ocean acidification during this period.The Cretaceous-Palaeogene(K/Pg)boundary at Bidart(France)is preceded by a~0.5 m thick interval with geochemical and taphonomic vestiges of an ocean acidification event linked with Deccan volcanism.New planktic foraminifera census and morphometric data now confirm biotic stress conditions related to acidification in the Deccan benchmark interval.The absolute abundance data of larger(>150μm)heavily calcified planktic morphogroups show fluctuating populations throughout zone CF1(spanning the final~225 ky),lowest peaks within the Deccan benchmark,and a demographic collapse(>90%)at the K/Pg boundary.The analyzed species are generally reduced in size,with thinner test walls in this~0.5 m interval,indicating the likelihood of calcification stress as a contributor to the overall biotic stress.At the K/Pg boundary,maximum biotic stress is recorded in all the tested faunal proxies.A preliminary graphic correlation of zone CF1 at Bidart with the auxiliary GSSP at Elles(Tunisia)constrains the Deccan benchmark interval of high biotic stress to the final~58ky of the late Maastrichtian,culminating in the K/Pg mass extinction.The volcanogenic Hg peaks coincident with faunal and taphonomic evidence of ocean acidification strengthen the Deccan-related ocean acidification hypothesis.