Palynoflora from deccan volcano-sedimentary sequence (Cretaceous-Palaeogene transition) of central India: implications for spatio-temporal correlation

Abstract

The sedimentary beds associated with Deccan Continental Flood Basalt (DCFB) sequences exposed in the volcanic subprovinces of Jabalpur-Mandla-Chhindwara (JMC) regions of Madhya Pradesh and Nand-Dongargaon (N-D) basin and the adjoining areas to the west in Yeotmal-Nanded in Maharashtra were studied for their palynofloral analysis. The sediments were characterized palynologically and changes in the palynoflora are observed at different stratigraphic levels in a number of sections including several new intertrappean localities recorded in recent years. For the purpose of effective correlation of different subprovinces, palynofloras of some of the previously studied intertrappeans are also reviewed. Our studies suggest that before the start of the Deccan volcanic activity, the palynoflora found in the Lameta sediments, was dominated by gymnosperms-angiosperm association. The plant canopy consisted mainly of gymnosperms (Conifers and Podocarpaceae) whereas, the understory members were mostly of palms and herbs (Poaceae and Asteraceae). The eruption of Deccan volcanic flows severely affected the existing floral association and proved fatal for the well established plant community. The immediately overlying sediments associated with the earliest volcanic flows are dominated by pteridophytes and angiosperm taxa (Azolla cretacea, Aquilapollenites bengalensis, Ariadnaesporites sp., Gabonisporis vigourouxii and Triporoletes reticulatus). Higher up in the stratigraphic sequence, similar forms continued with simultaneous appearance of new taxa including Scabrastephanocolpites spp. At still higher stratigraphic levels, abundance of fungi especially the mycorrhizal fungi, concurrent with sharp decline in pollen/spore recovery was observed. In the culminating phase (i.e. Palaeocene) of Deccan volcanic history a new palynofloral assemblage of typical Palaeocene taxa (Dandotiaspora dilata, D. pseudoauriculata, D. plicata, Spinizonocolpites echinatus, Matanomadhiasulcites sp., and Lakiapollis ovatus) was encountered.

Late Cretaceous origin of the rice tribe provides evidence for early diversification in Poaceae

“…These deposits are known for their wealth of fossils, including dinosaur bones, coprolites, egg-shell fragments, remains of turtles, frogs, fishes and mammals, as well as macro-and micro-floral remains [23][24][25] . Continued sampling 22,26,27 both from Lameta Formation sediments and associated titanosaurid sauropod coprolites from Pisdura (east and south sections) and sediments of the Lameta Formation at Dhamni, Piraya and Polgaon has yielded grass pollen and additional leaf cuticle with embedded grass silica short cell (GSSC) phytoliths similar to those found in oryzoid grasses (often referred to as 'oryzoid' silica bodies 28 ). Here we report on these newly recovered fossil cuticles and associated phytoliths (referred to as morphotypes Changii indicum and Tateokai deccana) and use them to suggest a different scenario and timing for the emergence and diversification of the rice tribe than what is widely assumed among evolutionary biologists.…”

Palaeoenvironmental changes associated with Deccan volcanism, examples from terrestrial deposits from Central India

“…The subsequent deposits are marked by floral recovery (Samant and Mohabey 2009;2014). 4) The organic matter content is very low in all infratrappean and intertrappean sediments, except in Governmental Well (phase-1) and in Podgawan section (phase-2).…”

“…The Governmental Well sediments are equivalent to the Mohgaon Kalan Well sediments described by Samant and Mohabey (2009;2014).…”

“…The presence of thin carbonate layers within the clays, as well as the carbonate nodules, may be indicative of groundwater level fluctuations. Palynological (Samant and Mohabey, 2009;2014) and paleontological (Mohabey et al, 1993;Mohabey and Udhoji, 1996) studies reveal the presence of a gymnosperm-angiosperm-rich palynoflora and a diversified fauna (turtles, frogs, crocodylomorphs, dinosaurs, etc. ).…”

“…Palynological studies indicate that immediately after the onset of Deccan phase-2, the pre-existing floral association was decimated leading to dominance by angiosperms and pteridophytes at the expense of gymnosperms. In subsequent early Paleocene intertrappean sediments of Podgawan, a sharp decrease in pollen and spores coupled with the dominance of Mycorrhizal fungi mark increasing stress conditions apparently as a direct result of volcanic activity (Samant and Mohabey, 2009;2014). The volcanic activity and the associated gas SO 2 , HCl (Self et al, 2008) changed the environmental conditions leading to strong volcanic influence and more acidic conditions.…”