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Deccan volcanism: A main trigger of environmental changes leading to the K/Pg mass extinction?

Authors:
Thierry Adatte at University of Lausanne
Thierry Adatte
Alicia Fantasia at University of Fribourg
Alicia Fantasia
Bandana Samant at Central University of Punjab
Bandana Samant
Dhananjay Mahendrakumar Mohabey at Formerly, Geological Survey of India
Dhananjay Mahendrakumar Mohabey
  • Formerly, Geological Survey of India
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Abstract and Figures

Recent studies indicate that the bulk (80%) of Deccan trap eruptions occurred over a relatively short time interval in magnetic polarity C29r, whereas multi-proxy studies from central and southeastern India place the Cretaceous-Paleogene (K/Pg) mass extinction near the end of this main phase of Deccan volcanism suggesting a cause-and-effect relationship. Beyond India multi-proxy studies also place the main Deccan phase in the uppermost Maastrichtian C29r below the K/Pg (planktic foraminiferal zones CF2-CF1), as indicated by a rapid shift in ¹⁸⁷Os/¹⁸⁸Os ratios in deep-sea sections from the Atlantic, Pacific and Indian Oceans, coincident with rapid climate warming, coeval increase in weathering, a significant decrease in bulk carbonate indicative of acidification due to volcanic SO2, and major biotic stress conditions expressed in species dwarfing and decreased abundance in calcareous microfossils (planktic foraminifera and nannofossils).
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STRATA, 2013, série 1, vol. 14. Pre-Cenozoic climates Workshop (PC2IW)
5
Multiproxy Evidence of main Deccan Volcanic Pulse near the
Cretaceous-Tertiary Boundary
Thierry Adatte1, Alicia Fantasia1, Bandana Samant2, Gerta Keller3, Hassan
Khozyem1 & Brian Gertsch4
1ISTE, Lausanne University, 1015 Lausanne, Switzerland; E-Mail: Thierry.adatte@unil.ch
2Department of Geology, Nagpur University, Nagpur 440 001, India; E-Mail: bandanabhu@gmail.com
3Department of Geosciences, Princeton University, Princeton NJ 08540, USA; E-Mail: Gkeller@princeton.edu
4Earth, Atmospheric and Planetary Science Department, MIT, Cambridge MA 02139, USA; E-Mail:
bgertsch@mit.edu
Model results predict that Deccan Traps emplacement was responsible for a strong increase in atmospheric
pCO2 accompanied by rapid warming of 4°C (Dessert et al., 2001, 2003) that was followed by global
cooling. During the warming phase, increased continental weathering of silicates associated with
consumption of atmospheric CO2 likely resulted in the drawdown of greenhouse gases that reversed the
warming trend leading to global cooling at the end of the Maastrichtian. Massive CO2 input together with
massive release of SO2 may thus have triggered the mass extinctions in the marine realm as a result of
ocean acidification leading to a carbon crisis and in the terrestrial realms due to acid rains (Fig. 1). Global
stress conditions related to these climatic changes are well known and documented in planktic foraminifera
by a diversity decrease, species dwarfing, dominance of opportunistic species and near disappearance of
specialized species (review in Keller and Abramovich, 2009).
Fig. 1: Flow chart for the model of massive Deccan volcanism as a main trigger of environmental changes
leading to the KTB mass extinction.
Recent studies indicate that the bulk (80%) of Deccan trap eruptions (phase-2) occurred over a relatively
short time interval in magnetic polarity C29r (Chenet et al., 2007). Multiproxy studies from central and
southeastern India place the Cretaceous-Tertiary (KT) mass extinction near the end of this main phase of
Deccan volcanism suggesting a cause-and effect relationship (Keller et al., 2008, 2012).
In India a strong floral response is observed as a direct response to Deccan volcanic phase-2. In Lameta
(infra-trapean) sediments preceding the volcanic eruptions, palynoflora are dominated by gymnosperms and
angiosperms with a rich canopy of gymnosperms (Conifers and Podocarpaceae) and an understory of
palms and herbs (Samant & Mohabey, 2005; Samant et al., 2008). Immediately after the onset of Deccan
phase-2, this floral association was decimated leading to dominance by angiosperms and pteridophytes at
the expense of gymnosperms.
In subsequent intertrappean sediments a sharp decrease in pollen and spores coupled with the appearance of
fungi mark increasing stress conditions apparently as a direct result of volcanic activity. The inter-trappean
STRATA, 2013, série 1, vol. 14. Pre-Cenozoic climates Workshop (PC2IW)
6
Fig. 2: Ti/Al ratio, Chemical Index of Alteration (CIA), basalt weathering intensity (K/Fe+Mg) in infra and
inter-trappean sediments, comparison with palynological data.
STRATA, 2013, série 1, vol. 14. Pre-Cenozoic climates Workshop (PC2IW)
7
sediments corresponding to Phase-2 (80% of Deccan basalt emissions, latest Maastrichtian) are
characterized by the highest Chemical Index of Alteration (CIA) values (Fig.2). This can be explained by
increased acid rains due to SO2 emissions rather than a global climatic shift, because clay minerals from the
corresponding sediments do not reflect a significant climate change. The increased weathering is coeval
with the sharp decline in pollen and an increase in fungal spores observed by Samant & Mohabey (2009)
and corresponds to the main phase-2 of Deccan activity. Values of K/(Fe+Mg) are very high in the final
Deccan phase-3 of the early Danian suggesting ongoing alteration of huge amounts of basalt.
Beyond India, multiproxy studies also place the main Deccan phase in the uppermost Maastrichtian C29r
below the KTB (planktic foraminiferal zones CF2-CF1 spanning 120ky and 160ky respectively), as
indicated by a rapid shift in 187Os/188Os ratios in deep-sea sections from the Atlantic, Pacific and Indian
Oceans (Robinson et al., 2009), coincident with rapid climate warming, coeval increase in weathering, a
significant decrease in bulk carbonate indicative of acidification due to volcanic SO2, and major biotic
stress conditions expressed in species dwarfing and decreased abundance in calcareous microfossils
(planktic foraminifera and nannofossils). These observations indicate that Deccan volcanism played a key
role in increasing atmospheric CO2 and SO2 levels that resulted in global warming and acidified oceans,
which led to increased biotic stress that predisposed faunas to eventual extinction at the KTB.
References
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Dessert C., Dupré B., François L.M., Schott J., Gaillardet J., Chakrapani G.J. & Bajpai S. (2001). Erosion of Deccan
Traps determined by river geochemistry: impact on the global climate and the 87Sr/86Sr ratio of seawater. Earth
and Planetary Science Letters, 188: 459– 474.
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environmental stress. Palaeogeography, Palaeoclimatology, Palaeoecology, 284: 47-62.
Keller G., Adatte T., Gardin S., Bartolini A. & Bajpai S. (2008). Main Deccan volcanism phase ends at K-T mass
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the Krishna-Godavari Basin, India. Earth and Planetary Science Letters, 341: 211-221.
Robinson N., Ravizza G., Coccioni R., Peucker-Ehrenbrink B. & Norris R. (2009). A high-resolution marine
187Os/188Os record for the late Maastrichtian: Distinguishing the chemical fingerprints of Deccan volcanism and
the KP impact event. Earth and Planetary Science Letters, 281: 159-168.
Samant B. & Mohabey D. M. (2005). Response of flora to Deccan volcanism: a case study from Nand-Dongargaon
basin of Maharashtra, implications to environment and climate. Gondwana Geological Magazin, 8: 151–164.
Samant B., Mohabey D. & Kapgate D.K. (2008). Palynofloral record from Singpur intertrappean, Chhindwara district,
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... The DVP of India hosts these sedimentary deposits mostly along its periphery (Kapur and Khosla, 2018) in the form of intra-, intertrappeans which preserves the evidences of the influence of volcanism on the biota, climate and sedimentary systems (Cripps et al., 2005). The intertrappeans of the DVP are extensively studied by Hislop (1860); Sahni et al. (1984); Prasad and Khajuria (1995); Singh (2000); Cripps et al. (2005); ; Adatte et al. (2014); Font et al. (2016); Keller et al. (2018); Prasad et al. (2018); Kapur and Khosla (2019) and many more. ...
... (b) Geological map of Saurashtra (modified after Khan and Ahmad, 1998) with studied sections of intra-, intertrappeans, 1. Ninama hill section (N 22° 18' 14.58";E 71° 19' 46.272";2.Ninama Sukhbhadar stream (N 22° 17' 59.73"; E 71° 20' 03.66"); 3. Ninama well section (N 22° 18' 11.81"; E 71° 19' 59.19 volcanologists, locally (Prakash, 1960;Ambwani, 1982;Ashok Sahni et al., 1984;Mukhopadhyay and Shome, 1996;Tandon, 2002;Srivastava et al., 2017;Keller et al., 2018) as well as globally (Assefa and Saxena, 1984;Williamson and Bell, 1994;Jolly, 1997;Durant, 2006;Abbate et al., 2014). It is necessary to define them formally Parthasarathy et al., 2008;Srivastava et al., 2017), Bamanbor and Ninama (Fedden, 1884;Borkar, 1973Borkar, , 1975Borkar, , 1984Shringarpure, 1985;Adatte et al., 2014;Samant et al., 2014). ...
... The typical DVP sedimentary deposits have limited thickness, lateral extent, patchy nature, and variable lithology, which hinder correlation and limit their usefulness in stratigraphic subdivisions. (Prasad and Khajuria, 1990;Prasad and Singh, 1991;Khadkikar et al., 1999;Khosla and Sahni, 2003;Chenet et al., 2008;Keller et al., 2009Keller et al., , 2012Keller et al., , 2018Malarkodi et al., 2010;Bajpai et al., 2013;Adatte et al., 2014;Prasad andSahni, 2014b, 2014a;Smith et al., 2015;Font et al., 2016;Kapur et al., 2018;Mohabey and Samant, 2019;Kapur and Khosla, 2019;Samant et al., 2020). The first attempt was made by Sahni et al. (1984) to formalise the Nagpur Intertrappean, assigning Takli Formation, but its discontinuous nature succumbed their identity. ...
Lithostratigraphy of the Paleogene Deccan Intra-, Intertrappeans of the Saurashtra, Western India and their Prevalence in Large Igneous Provinces
Article
  • Sep 2023
  • J GEOL SOC INDIA
The periphery of the Deccan Volcanic Province (DVP) of India comprises sedimentary succession deposited during the waning phase of volcanism across the Cretaceous-Paleogene boundary which preserves the continental biota. The Saurashtra Peninsula, a part of the Saurashtra-Kachchh sub-province, exposes thick intertrappean sedimentary successions, systematically described to understand the stratigraphic framework with respect to the lava flows and their geographic distinctness. The thickness of the exposed sections is measured, and contact and continuities are marked, revealing two different, small geographically isolated but adjacent, coeval basins, named the Ninama Basin and Chotila Basin, initially comprising fine grain sediment, followed by thick conspicuous limestone and chert deposits respectively. Formal lithostratigraphic unit names are proposed for both basins: Ninama Basin comprises lithic arenite, fossiliferous limestone, bedded siltstone, mudstone and claystone, and is divided into Sukhbhadar Formation and Ninama Limestone. Chotila Basin comprises calcareous sandstone, bedded siltstone, silty shale and mudstone, claystone and chert divided into Rangpar Formation, Chotila Chert, and Bamanbor Formation. Lithology and palynofossil evidence suggest restricted continental environments with varying salinities during the Paleogene.
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... Though not a scientist, his work is often forgotten, but his ideas were extended by Chamberlin (1897) who must be regarded as the first geoscientist to attempt the link between atmospheric pCO 2 and climate, a debate that continues today. In the longer term (climate rather than weather), the CO 2 erupted normally causes warming, as evidenced by the Deccan Traps in the latest Cretaceous and earliest Paleogene (Courtillot & Renne 2003;Chenet et al. 2007Chenet et al. , 2009Adatte et al. 2014;Keller 2014;Punekar et al. 2014;Schoene et al. 2015). ...
The 'Black Band': Local expression of a global event
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  • Apr 2018
The organic-rich, black mudstones that were initially described as the Black Band in Lincolnshire, Humberside and Yorkshire are known to be a local representation of the Cenomanian-Turonian Boundary Event (CTBE). This world-wide event is known as Oceanic Anoxic Event ll (OAEll) and it marks a distinctive extinction event within the Cretaceous biota. Since some of the original work on the benthic foraminifera that are found in both the Black Band and coeval sedimentary rocks, there has been a significant increase in the understanding of the biology of foraminifera, and their response to both modern and fossil low-O2 environments. While the overall event is clearly global, the local response appears to be a function of both geological setting and water depth with the occurrence of organic-rich sediments as a combination of this setting, plankton productivity and preservation. © 2018 The Author(s). Published by The Geological Society of London for the Yorkshire Geological Society. All rights reserved.
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Origin and Evolution of Birds
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  • Nov 2023
Archaeopteryx lived about 155 million years ago and was a descendent of a long line of dinosaur and theropod ancestors. In this chapter, I review current ideas about the evolution of birds and discuss in detail how dinosaurs eventually gave rise to birds and why birds are considered to be dinosaurs. Over millions of years of dinosaur and theropod evolution, body sizes declined and limb lengths changed and theropods became more bird-like. Factors that likely contributed to such changes are described in detail. How and why, during the evolution of birds, natural selection might have favored changes in digestive systems, including the loss of teeth, and reproductive systems is also explained. Information about the first birds, including Archaeopteryx, jeholornithids, confuciusornithids, sapeornithids, enantiornithids, and ornithuromorphs, is provided. Possible reasons why the ancestors of present-day birds survived the end-Cretaceous extinction event are also provided. Finally, I describe how birds quickly diversified after that extinction event and ultimately gave rise to the thousands of species of present-day birds.
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Palynofloral record from Singpur Intertrappean, Chhindwara District Madhya Pradesh: Implication for Late Cretaceous stratigraphic correlation and resolution
Article
Full-text available
  • Jun 2008
  • J GEOL SOC INDIA
A diversified palynoassemblage has been recorded from the Singpur intertrappean of Chhindwara District, Madhya Pradesh, that has earlier yielded megafloral remains. The section is strategic as it is located between the Chhindwara-Mandla-Jabalpur (CMJ) sector to the north and Nand-Dongargaon (ND) basin to the south, that have so far produced a majority of the palynologically studied intertrappean sections associated with the Deccan Volcanic Sequence (DVS). In this context the palynological assessment of the Singpur inter-trappean is critical for establishing a spatio-temporal correlations of the sediments of the two widely separated volcanic sub-provinces/regions. The Singpur palynoassemblage shows presence of marker Late Cretaceous (Maastrichtian) palynotaxa viz. Aquilapollenites bengalensis, Ariadnaesporites sp., Gabonisporis spp. and Pulcheripollenites cauveriana, associated with primitive stephanocolpate pollen. The appearance of polyaperturate pollen grains in the central India is significant as it suggests the evolutionary trend in the angiosperms during Latest Cretaceous. The overall assemblage of the Singpur is indicated to be coeval with the Sindhi intertrappean bed of ND basin, and younger than the dinosaur bearing intertrappean beds of Mohagaon kalan (well section) and Ranipur of CMJ sector in the north. It is also indicated that the famous iridium bearing intertrappean section at Anjar (Kutch) associated with dinosaurs (Titanosaurus indicus) and deposited during 29 R, is older to the Singpur intertrappean bed.
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Nature and timing of extinctions in Cretaceous-Tertiary planktic foraminifera preserved in Deccan intertrappean sediments of the Krishna–Godavari Basin, India
Article
  • Aug 2012
  • EARTH PLANET SC LETT
In C29r below the Cretaceous-Tertiary boundary (KTB) massive Deccan Trap eruptions in India covered an area the size of France or Texas and produced the world’s largest and longest lava megaflows 1500 km across India through the Krishna–Godavari (K–G) Basin into the Bay of Bengal. Investigation of ten deep wells from the K–G Basin revealed four lava megaflows separated by sand, silt and shale with the last megaflow ending at or near the KTB. The biologic response in India was swift and devastating. During Deccan eruptions prior to the first megaflow, planktic foraminifera suffered 50% species extinctions. Survivors suffered another 50% extinctions after the first megaflow leaving just 7–8 species. No recovery occurred between the next three megaflows and the mass extinction was complete with the last mega-flow at or near the KTB. The last phase of Deccan volcanism occurred in the early Danian C29n with deposition of another four megaflows accompanied by delayed biotic recovery of marine plankton. Correlative with these intense volcanic phases, climate changed from humid/tropical to arid conditions and returned to normal tropical humidity after the last phase of volcanism. The global climatic and biotic effects attributable to Deccan volcanism have yet to be fully investigated. However, preliminary studies from India to Texas reveal extreme climate changes associated with high-stress environmental conditions among planktic foraminifera leading to blooms of the disaster opportunist Guembelitria cretacea during the late Maastrichtian.
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40K-40Ar dating of the Main Deccan large igneous province: Further evidence of KTB age and short duration
Article
  • Nov 2007
  • EARTH PLANET SC LETT
Most mass extinctions coincide in time with outpourings of continental flood basalts (CFB). Some 20 years ago, it was shown [Courtillot, V., Besse, J., Vandamme, D., Montigny, R., Jaeger, J.-J., Cappetta, H., 1986. Deccan flood basalts at the Cretaceous/Tertiary boundary? Earth Planet. Sci. Lett. 80, 361–374; Courtillot, V., Feraud, G., Maluski, H., Vandamme, D., Moreau, M.G., Besse, J., 1988. Deccan flood basalts and the Cretaceous/Tertiary boundary. Nature 333, 843–846; Duncan, R.A., Pyle, D.G., 1988. Rapid eruption of the Deccan flood basalts at the Cretaceous/Tertiary boundary. Nature 333 841–843] that the age of the Deccan traps was close to the Cretaceous–Tertiary (KT) boundary and its duration under 1 Myr. We have undertaken a new geochronological study, using the (unconventional) 40K–40Ar Cassignol–Gillot technique which is particularly well suited to the potassium-poor Deccan lavas. The mean of 4 determinations from the topmost (Ambenali and Mahabaleshwar) Formations is 64.5±0.6 Ma. They straddle the C29r/C29n reversal boundary for which they provide a new constraint. The mean age of 3 determinations from the oldest (Jawhar) Formation is 64.8±0.6 Ma. The difference in age between top and bottom of a 3500 m composite section, probably comprising 80% of the total Deccan volume, is statistically insignificant, with the overall mean age being 64.7±0.6 Ma (N=7). Our results are consistent with the most recent 40Ar/39Ar determinations [Knight, K.B., Renne, P.R., Halkett, A., White, N., 2003. 40Ar/ 39Ar dating of the Rajahmundry Traps, eastern India and their relationship to the Deccan traps. Earth Planet. Sci. Lett. 208, 85–99; Knight, K.B., Renne, P.R., Baker, J., Waight, T., White, N., 2005. Reply to ‘40Ar/39Ar dating of the Rajahmundry Traps, Eastern India and their relationship to the Deccan Traps: Discussion’ by A.K. Baksi. Earth Planet. Sci. Lett. 239, 374–382], confirming that there should be no systematic difference between the two methods when they are used in an optimal way. An earlier, smaller but significant, pulse of volcanism between 68 and 67 Ma, extending over at least 500 km in latitude in the northern part of the Deccan CFB has also been identified. After 2 to 3 Ma of quiescence, the second, major phase of volcanism occurred near 65 Ma, expanding over most of the area covered by the first pulse and another 500 km to the South, consistent with drift of India by 300 to 450 km at ∼150 mm/yr during the quiescence period. New paleontological data from the remote Rajahmundry section [Keller, G., Adatte, T., Gardin, S., Bartolini, A., Bajpai, S., Humler, E., in prep. The Cretaceous–Tertiary boundary in Deccan Traps of the Krishna–Godavari Basin of southeastern India. EPSL to be submitted] suggest that this second pulse can itself be divided into two major pulses, one starting in C29r and ending at the KT boundary, the second starting in the upper part of C29r and ending within C29n.
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Lilliput effect in late Maastrichtian planktic foraminifera: Response to environmental stress
Article
  • Oct 2009
  • PALAEOGEOGR PALAEOCL
The Lilliput effect marks morphologic and intraspecies size reductions in response to environmental stresses commonly associated with the aftermath of mass extinctions. This study shows that the Lilliput effect is a universal biotic response associated with greenhouse warming, mesotrophic or restricted basins, shallow marginal settings and volcanically active regions during the late Maastrichtian. Sedimentary sequences analyzed from Tunisia, Egypt, Texas, Argentina, the South Atlantic and Indian Ocean reveal that the biotic stress response appears uniform, regardless of the cause, varying only with the degree of biotic stress. Overall, late Maastrichtian environments span a continuum from optimum conditions to the catastrophic (mass extinctions) with a predictable set of biotic responses relative to the degree of stress induced by oxygen, salinity, temperature and nutrient variations as a result of climate and sea level changes and volcanism. Early stages of biotic stress result in diversity reduction and the elimination of large specialized species (k-strategists) leading to morphologic size reduction via selective extinction/disappearances and intraspecies dwarfing of survivors. Later stages of biotic stress result in the complete disappearance of k-strategists, intraspecies dwarfing of r-strategists and dominance by low oxygen tolerant small heterohelicids. At the extreme end of the biotic response are volcanically influenced environments, which cause the same detrimental biotic effects as observed in the aftermath of the K–T mass extinction, including the disappearance of most species and blooms of the disaster opportunist Guembelitria.
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Erosion of Deccan Traps determined by river geochemistry: Impact on the global climate and the 87Sr/86Sr ratio of seawater
Article
  • Jun 2001
  • EARTH PLANET SC LETT
The impact of the Deccan Traps on chemical weathering and atmospheric CO2 consumption on Earth is evaluated based on the study of major elements, strontium and 87Sr/86Sr isotopic ratios of the main rivers flowing through the traps, using a numerical model which describes the coupled evolution of the chemical cycles of carbon, alkalinity and strontium and allows one to compute the variations in atmospheric pCO2, mean global temperature and the 87Sr/86Sr isotopic ratio of seawater, in response to Deccan trap emplacement. The results suggest that the rate of chemical weathering of Deccan Traps (21–63 t/km2/yr) and associated atmospheric CO2 consumption (0.58–2.54×106 mol C/km2/yr) are relatively high compared to those linked to other basaltic regions. Our results on the Deccan and available data from other basaltic regions show that runoff and temperature are the two main parameters which control the rate of CO2 consumption during weathering of basalts, according to the relationship:
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A high-resolution marine 187Os/188Os record for the late Maastrichtian: Distinguishing the chemical fingerprints of Deccan volcanism and the KP impact event
Article
  • May 2009
  • EARTH PLANET SC LETT
A composite late Maastrichtian (65.5 to 68.5 Ma) marine osmium (Os) isotope record, based on samples from the Southern Ocean (ODP Site 690), the Tropical Pacific Ocean (DSDP Site 577), the South Atlantic (DSDP Site 525) and the paleo-Tethys Ocean demonstrates that subaerially exposed pelagic carbonates can record seawater Os isotope variations with a fidelity comparable to sediments recovered from the seafloor. New results provide robust evidence of a 20% decline in seawater 187Os/188Os over a period of about 200 kyr early in magnetochron C29r well below the Cretaceous–Paleogene Boundary (KPB), confirming previously reported low-resolution data from the South Atlantic Ocean. New results also confirm a second more rapid decline in 187Os/188Os associated with the KPB that is accompanied by a significant increase in Os concentrations. Complementary platinum (Pt) and iridium (Ir) concentration data indicate that the length scale of diagenetic remobilization of platinum group elements from the KPB is less than 1 m and does not obscure the pre-KPB decline in 187Os/188Os. Increases in bulk sediment Ir concentrations and decreases in bulk carbonate content that coincide with the Os isotope shift suggest that carbonate burial flux may have been lower during the initial decline in 187Os/188Os. We speculate that diminished carbonate burial rate may have been the result of ocean acidification caused by Deccan volcanism.
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Main Deccan volcanism phase ends near the K–T boundary: Evidence from the Krishna–Godavari Basin, SE India
Article
  • Apr 2008
  • EARTH PLANET SC LETT
Recent studies indicate that the bulk (80%) of the Deccan trap eruptions occurred over less than 0.8 m.y. in magnetic polarity C29r spanning the Cretaceous–Tertiary (K–T) boundary. Determining where within this major eruptive phase the K–T mass extinction occurred has remained problematic. For this reason, models estimating the biotic and environmental consequences have generally underestimated the rate and quantity of Deccan gas emissions by orders of magnitude leading to conclusions that volcanism could not have been one of the major causes for the K–T mass extinction. In this study we report that the most massive Deccan trap eruption occurred near the K–T mass extinction.These results are based on sedimentologic, microfacies and biostratigraphic data of 4–9 m thick intertrappean sediments in four quarry outcrops in the Rajahmundry area of the Krishna–Godavari Basin of southeastern India. In this area two Deccan basalt flows, known as the Rajahmundry traps, mark the longest lava flows extending 1500 km across the Indian continent and into the Bay of Bengal. The sediments directly overlying the lower Rajahmundry trap contain early Danian planktic foraminiferal assemblages of zone P1a, which mark the evolution in the aftermath of the K–T mass extinction. The upper Rajahmundry trap was deposited in magnetic polarity C29n, preceding full biotic recovery. These results suggest that volcanism may have played critical roles in both the K–T mass extinction and the delayed biotic recovery.
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