GERTA KELLER TOPICAL PUBLICATIONS

Deccan Volcanism

Deccan volcanism, the Chicxulub impact, and the end-Cretaceous mass extinction: Coincidence? Cause and effect?

TitleDeccan volcanism, the Chicxulub impact, and the end-Cretaceous mass extinction: Coincidence? Cause and effect?
Publication TypeBook Chapter
Year of Publication2014
AuthorsKeller, G
Book TitleVolcanism, Impacts, and Mass Extinctions: Causes and Effects
Volume505
EditionGSA Special Papers
PaginationPp. 29-55
PublisherGeological Society of America
CityBoulder
Abstract

The recent discovery of the direct link between Deccan volcanism and the end-Cretaceous mass extinction also links volcanism to the late Maastrichtian rapid global warming, high environmental stress, and the delayed recovery in the early Danian. In comparison, three decades of research on the Chicxulub impact have failed to account for long-term climatic and environmental changes or prove a coincidence with the mass extinction. A review of Deccan volcanism and the best age estimate for the Chicxulub impact provides a new perspective on the causes for the end­Cretaceous mass extinction and supports an integrated Deccan-Chicxulub scenario. This scenario takes into consideration climate warming and cooling, sea-level changes, erosion, weathering, ocean acidification, high-stress environments with opportunistic species blooms, the mass extinction, and delayed postextinction recovery.The crisis began in C29r (upper CF2 to lower CF1) with rapid global warming of 4 °C in the oceans and 8 °C on land, commonly attributed to Deccan phase 2 eruptions. The Chicxulub impact occurred during this warm event (about 100–150 k.y. before the mass extinction) based on the stratigraphically oldest impact spherule layer in NE Mexico, Texas, and Yucatan crater core Yaxcopoil-1. It likely exacerbated climate warming and may have intensified Deccan eruptions. The reworked spherule layers at the base of the sandstone complex in NE Mexico and Texas were deposited in the upper half of CF1,  50–80 k.y. before the Cretaceous-Tertiary (K-T) boundary. This sandstone complex, commonly interpreted as impact tsunami deposits of K-T boundary age, was deposited during climate cooling, low sea level, and intensified currents, leading to erosion of nearshore areas (including Chicxulub impact spherules), transport, and redeposition via submarine channels into deeper waters. Renewed climate warming during the last  50 k.y. of the Maastrichtian correlates with at least four rapid, massive volcanic eruptions known as the longest lava flows on Earth that ended with the mass extinction, probably due to runaway effects. The kill mechanism was likely ocean acidification resulting in the carbonate crisis commonly considered to be the primary cause for four of the five Phanerozoic mass extinctions.  PDF

URLhttp://specialpapers.gsapubs.org/content/early/2014/06/10/2014.2505_03.1.abstract
DOI10.1130/2014.2505(03)

Effects of Deccan volcanism on paleoenvironment and planktic foraminifera: A global survey

TitleEffects of Deccan volcanism on paleoenvironment and planktic foraminifera: A global survey
Publication TypeJournal Article
Year of Publication2014
AuthorsPunekar, J, Mateo, P, Keller, G
JournalGeological Society of America Special Papers
Volume505
Abstract

Deccan volcanism, one of Earth's largest flood basalt provinces, erupted  80% of its total volume (phase 2) during a relatively short time in the uppermost Maastrichtian paleomagnetic chron C29r and ended with the Cretaceous-Tertiary boundary mass extinction. Full biotic recovery in the marine realm was delayed at least 500 k.y. or until after the last Deccan eruptions in C29n (phase 3, 14% of the total Deccan volume). For over 30 yr, the mass extinction has been commonly attributed to the Chicxulub impact, and the delayed recovery remained an enigma. Here, we demonstrate that the two phases of Deccan volcanism can account for both the mass extinction and delayed marine recovery.In India, a direct correlation between Deccan eruptions (phase 2) and the mass extinction reveals that  50% of the planktic foraminifer species gradually disappeared during volcanic eruptions prior to the first of four lava megaflows, reaching  1500 km across India, and out to the Bay of Bengal. Another 50% disappeared after the first megaflow, and the mass extinction was complete with the last megaflow. Throughout this interval, blooms of the disaster opportunist Guembelitria cretacea dominate shallow-marine assemblages in coeval intervals from India to the Tethys and the Atlantic Oceans to Texas. Similar high-stress environments dominated by blooms of Guembelitria and/or Globoconusa are observed correlative with Deccan volcanism phase 3 in the early Danian C29n, followed by full biotic recovery after volcanism ended. The mass extinction and high-stress conditions may be explained by the intense Deccan volcanism leading to rapid global warming and cooling in C29r and C29n, enhanced weathering, continental runoff, and ocean acidification, resulting in a carbonate crisis in the marine environment.  PDF

URLhttp://specialpapers.gsapubs.org/content/early/2014/08/21/2014.2505_04.abstract
DOI10.1130/2014.2505(04)

Late Maastrichtian–early Danian high-stress environments and delayed recovery linked to Deccan volcanism

TitleLate Maastrichtian–early Danian high-stress environments and delayed recovery linked to Deccan volcanism
Publication TypeJournal Article
Year of Publication2014
AuthorsPunekar, J, Keller, G, Khozyem, H, Hamming, C, Adatte, T, Tantawy, AAAM, Ponte, J
JournalCretaceous Research
Volume49
Pagination63 - 82
Date PublishedJan-05-2014
ISSN01956671
Abstract

Deccan volcanism occurred in three intense phases of relatively short duration: phase 1 spanning the paleomagnetic chron C30r/C30n boundary (planktic foraminiferal CF4), phase 2 in the latest Maastrichtian C29r (zones CF1–CF2), and phase 3 in the early Danian C29n (P1b). This study explores the nature of paleoenvironmental changes correlative with the three volcanic phases in central Egypt and the Sinai based on planktic foraminifers, stable carbon and oxygen isotopes.

Results show that high-stress assemblages dominated by Guembelitria blooms are prominent in, but not exclusive to, all three volcanic phases. These blooms are well known from the aftermath of this mass extinction in zones P0–P1a, the intertrappean interval between volcanic phases 2 and 3. Guembelitria blooms in CF4 (phase 1) are relatively minor (<45%) although they comprise a substantial component of the planktic foraminiferal assemblages. Maximum Guembelitria blooms (>80% of the total assemblage) are observed in CF1, which spans the last 160 ka of the Maastrichtian marked by rapid global climatic warming and cooling correlative with phase 2. Major Guembelitria blooms (50–75%) are also observed in P1b, which is marked by climate warming (Dan-C2 event) and a major negative carbon isotope excursion correlative with phase 3. This high-stress event precedes full marine biotic recovery after the mass extinction.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0195667114000056
DOI10.1016/j.cretres.2014.01.002
Short TitleCretaceous Research

Atmospheric halogen and acid rains during the main phase of Deccan eruptions: Magnetic and mineral evidence

TitleAtmospheric halogen and acid rains during the main phase of Deccan eruptions: Magnetic and mineral evidence
Publication TypeBook Chapter
Year of Publication2014
AuthorsFont, E, F. Sebastien, S, Nédélec, A, Adatte, T, Keller, G, Veiga-Pires, C, Ponte, J, Mirão, J, Khozyem, H, Spangenberg, J
Book TitleVolcanism, Impacts, and Mass Extinctions: Causes and Effects: Geological Society of America Special Paper 505
PaginationPp. 353–368
PublisherGeological Society of America
CityBoulder
Abstract

Environmental changes linked to Deccan volcanism are still poorly known. A major limitation resides in the paucity of direct Deccan volcanism markers and in the geologically short interval where both impact and volcanism occurred, making it hard to evaluate their contributions to the mass extinction. We investigated the low-magnetic-susceptibility interval just below the iridium-rich layer of the Bidart (France) section, which was recently hypothesized to be the result of paleoenvironmental perturbations linked to paroxysmal Deccan phase 2. Results show a drastic decrease of detrital magnetite and presence of scarce akaganeite, a hypothesized reaction product formed in the aerosols derived from reaction of a volcanic plume with water and oxygen in the high atmosphere. A weathering model of the consequences of acidic rains on a continental regolith reveals nearly complete magnetite dissolution after ~31,000 yr, which is consistent with our magnetic data and falls within the duration of the Deccan phase 2. These results highlight the nature and importance of the Deccan-related environmental changes leading up to the end-Cretaceous mass extinction. PDF

URLhttp://specialpapers.gsapubs.org/content/current
DOI10.1130/2014.2505(18)

U-Pb geochronology of the Deccan Traps and relation to the end-Cretaceous mass extinction

TitleU-Pb geochronology of the Deccan Traps and relation to the end-Cretaceous mass extinction
Publication TypeJournal Article
Year of Publication2014
AuthorsSchoene, B, Samperton, KM, Eddy, MP, Keller, G, Adatte, T, Bowring, SA, Khadri, SFR, Gertsch, B
JournalScience
Date PublishedNov-12-2014
ISSN0036-8075
Abstract

The Chicxulub asteroid impact (Mexico) and the eruption of the massive Deccan volcanic province (India) are two proposed causes of the end-Cretaceous mass extinction, which includes the demise of nonavian dinosaurs. Despite widespread acceptance of the impact hypothesis, the lack of a high-resolution eruption timeline for the Deccan basalts has prevented full assessment of their relationship to the mass extinction. Here we apply U-Pb zircon geochronology to Deccan rocks and show that the main phase of eruptions initiated ~250,000 years before the Cretaceous-Paleogene boundary and that >1.1 million km3 of basalt erupted in ~750,000 years. Our results are consistent with the hypothesis that the Deccan Traps contributed to the latest Cretaceous environmental change and biologic turnover that culminated in the marine and terrestrial mass extinctions.   PDF

URLhttp://www.sciencemag.org/cgi/doi/10.1126/science.aaa0118
DOI10.1126/science.aaa0118
Short TitleScience

SPE505: Volcanism, Impacts, and Mass Extinctions: Causes and Effects

TitleSPE505: Volcanism, Impacts, and Mass Extinctions: Causes and Effects
Publication TypeBook
Year of Publication2014
AuthorsKeller, G, Kerr, AC
Series TitleGSA Special Papers
Volume505
PublisherGeological Society of America
CityBoulder
ISBN978-0-8137-2505-5
Abstract

The 26 chapters of this symposium volume encompass reviews of special topics, summaries of particular datasets and original research contributions. Together they span age intervals ranging from the Neoproterozoic, Mesozoic to Paleogene and Recent addressing a variety of stratigraphic, paleoecologic, environmental and paleoclimatic events. These contributions are organized under four themes: 1. Applications, 2. Paleoecology—Recent, 3. Global bioevents—PE and KTB, and 4. Biodiversity and Stratigraphy in Deep Time. 

URLhttp://specialpapers.gsapubs.org/content/current
DOI10.1130/9780813725055

Magnetic and mineral markers of atmospheric halogen and acid rains during the major Deccan episode

TitleMagnetic and mineral markers of atmospheric halogen and acid rains during the major Deccan episode
Publication TypeConference Paper
Year of Publication2013
AuthorsFont, E, Fabre, S, Nédélec, A, Adatte, T, Keller, G, Veiga-Pires, C, Ponte, J, Mirão, J, Khozyem, H, Spangenberg, J
Conference NameEGU General Assembly
Date Published2013
PublisherGeophysical Research Abstracts
Conference LocationVienna
Other NumbersVol. 15
KeywordsAcid Rain, akaganeite, deccan volcanism, mass extinction, rock magnetism and weathering model.
Abstract

Environmental changes linked to Deccan volcanism are still poorly known. A major limitation resides in the paucity of direct Deccan volcanism markers and in the geologically short interval where both impact and volcanism occurred, making it hard to evaluate their contributions to the mass extinction. We investigated the low magnetic susceptibility interval just below the Iridium-rich layer of the Bidart (France) section, which was recently hypothesized to be the result of palaeoenvironmental perturbations linked to paroxysmal Deccan phase-2. Results show a drastic decrease of detrital magnetite and presence of scarce akaganeite, a hypothesized reaction product formed in the aerosols derived from reaction of the volcanic plume with water and oxygen in the high atmosphere. A weathering model of the consequences of acidic rains on a continental regolith reveals nearly complete magnetite dissolution after about 31,000 years, which is consistent with our magnetic data and fall within the duration of the Deccan phase-2. These results highlight the nature and importance of the Deccan-related environmental changes leading up to the end-Cretaceous mass extinction.

URLhttp://www.frontiersin.org/profile/publications/24220227

Multiproxy evidence of main Deccan Traps pulse near the Cretaceous-Tertiary boundary

TitleMultiproxy evidence of main Deccan Traps pulse near the Cretaceous-Tertiary boundary
Publication TypeBook Chapter
Year of Publication2013
AuthorsAdatte, T, Keller, G
Book TitleProceedings of XXIII Indian Colloquium on Micropaloentology and Stratigraphy and International Symposium on Global Bioevents in Earth's History
Volume1
ChapterPart III, Pp. 243
EditionSpecial Publication
PublisherGeological Society of India
CityBangalore
ISBN978-93-80998-08-4
KeywordsGlobal Bioevents, KTB, PE
Abstract

Recent studies indicate that the bulk (80%) of Deccan trap eruptions occurred over a relatively short time interval in magnetic polarity C29r, whereas 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. Beyond India multiproxy studies also place the main Deccan phase in the uppermost Maastrichtian C29r below the KTB (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). 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, respectively, increasing biotic stress that predisposed faunas to eventual extinction at the KTB.

URLhttp://www.geosocindia.com/index.php?page=shop.product_details&flypage=flypage-ask.tpl&product_id=227&category_id=20&option=com_virtuemart&Itemid=6

Nature and timing of extinctions in Cretaceous-Tertiary planktic foraminifera preserved in Deccan intertrappean sediments of the Krishna–Godavari Basin, India

TitleNature and timing of extinctions in Cretaceous-Tertiary planktic foraminifera preserved in Deccan intertrappean sediments of the Krishna–Godavari Basin, India
Publication TypeJournal Article
Year of Publication2012
AuthorsKeller, G, Adatte, T, Bhowmick, PK, Upadhyay, H, Dave, A, Reddy, AN, Jaiprakash, BC
JournalEarth and Planetary Science Letters
Volume341-344
Pagination211 - 221
Date PublishedJan-08-2012
ISSN0012821X
Abstract

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.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0012821X12003056
DOI10.1016/j.epsl.2012.06.021
Short TitleEarth and Planetary Science Letters

Volcanism, impacts and mass extinctions (Long Version)

TitleVolcanism, impacts and mass extinctions (Long Version)
Publication TypeWeb Article
Year of Publication2012
AuthorsKeller, G, Armstrong, H, Courtillot, V, Harper, D, Joachimski, M, Kerr, A, MacLeod, N, Napier, W, Palfy, J, Wignall, P
Access Year2012
Access DateNovember
PublisherThe Geological Society
CityLondon
Type of MediumOnline version
Keywordsclimate change, Impacts, Mass extinctions, ocean anoxia, Phanerozoic, Volcanism
Abstract

The nature and causes of mass extinctions in the geological past have remained topics of intense scientific debate for the past three decades.  Central to this debate is the question of whether one or several large bolide impacts, the eruption of large igneous provinces (LIPS), or a combination of the two were the primary mechanism(s) driving the environmental and habitat changes that are universally regarded as the proximate causes for four of the five major extinction events.  Recent years have seen a revolution in our understanding of both the interplanetary environment and LIPS eruptions and their environmental effects such that the current impact-kill scenario no longer seems adequate for the KT (KPg) or any other mass extinction.  Massive sequential volcanic eruptions and the breakup of giant comets leading to rapid climate change, ocean anoxia and ozone destruction emerge as the leading causes in major mass extinctions.  PDF

URLhttp://www.geolsoc.org.uk/Geoscientist/Archive/November-2012/Volcanism-impacts-and-mass-extinctions-2
Alternate TitleVolcanism, impacts and mass extinctions (long version)

The Cretaceous–Tertiary Mass Extinction, Chicxulub Impact, and Deccan Volcanism

TitleThe Cretaceous–Tertiary Mass Extinction, Chicxulub Impact, and Deccan Volcanism
Publication TypeBook Chapter
Year of Publication2012
AuthorsKeller, G
Book TitleEarth and Life
Pagination759 - 793
PublisherSpringer Netherlands
CityDordrecht
ISBN Number978-90-481-3427-4
KeywordsChicxulub impact, Cretaceous, Danian, deccan volcanism, Foraminifers, Maastrichtian, Mass extinctions, Paleogene
Abstract

After three decades of nearly unchallenged wisdom that a large impact (Chicxulub) on Yucatan caused the end-Cretaceous mass extinction, this theory is facing its most serious challenge from the Chicxulub impact itself, as based on evidence in Texas and Mexico and from Deccan volcanism in India. Data generated from over 150 Cretaceous–Tertiary (KT) boundary sequences to date make it clear that the long-held belief in the Chicxulub impact as the sole or even major contributor to the KT mass extinction is not supported by evidence. The stratigraphic position of the Chicxulub impact ejecta spherules in NE Mexico and Texas and the impact breccia within the crater on Yucatan demonstrate that this impact predates the KTB by about 300,000 years. Planktic foraminiferal and stable isotope analyses across the primary impact ejecta layer reveal that not a single species went extinct as a result of this impact and no significant environmental changes could be determined. The catastrophic effects of this impact have been vastly overestimated. In contrast, recent advances in Deccan volcanic studies indicate three volcanic phases with the smallest at 67.5 Ma, the main phase at the end of the Maastrichtian (C29r), and the third phase in the early Danian C29r/C29n transition (Chenet et al. 2007). The main phase of eruptions occurred rapidly, was marked by the longest lava flows spanning 1500 km across India, and ended coincident with the KT boundary. The KT mass extinction may have been caused by these rapid and massive Deccan lava and gas eruptions that account for ∼80% of the entire 3500 m thick Deccan lava pile.

URLhttp://link.springer.com/content/pdf/10.1007/978-90-481-3428-1_25
DOI10.1007/978-90-481-3428-110.1007/978-90-481-3428-1_25

Deccan volcanism linked to the Cretaceous-Tertiary boundary mass extinction: New evidence from ONGC wells in the Krishna-Godavari Basin

TitleDeccan volcanism linked to the Cretaceous-Tertiary boundary mass extinction: New evidence from ONGC wells in the Krishna-Godavari Basin
Publication TypeJournal Article
Year of Publication2011
AuthorsKeller, G, Bhowmick, PK, Upadhyay, H, Dave, A, Reddy, AN, Jaiprakash, BC, Adatte, T
JournalJournal of the Geological Society of India
Volume78
Issue5
Pagination399 - 428
Date PublishedJan-11-2011
ISSN0016-7622
Abstract

A scientific challenge is to assess the role of Deccan volcanism in the Cretaceous-Tertiary boundary (KTB) mass extinction. Here we report on the stratigraphy and biologic effects of Deccan volcanism in eleven deep wells from the Krishna-Godavari (K-G) Basin, Andhra Pradesh, India. In these wells, two phases of Deccan volcanism record the world’s largest and longest lava mega-flows interbedded in marine sediments in the K-G Basin about 1500 km from the main Deccan volcanic province. The main phase-2 eruptions (∼80% of total Deccan Traps) began in C29r and ended at or near the KTB, an interval that spans planktic foraminiferal zones CF1–CF2 and most of the nannofossil Micula prinsii zone, and is correlative with the rapid global warming and subsequent cooling near the end of the Maastrichtian. The mass extinction began in phase-2 preceding the first of four mega-flows. Planktic foraminifera suffered a 50% drop in species richness. Survivors suffered another 50% drop after the first mega-flow, leaving just 7 to 8 survivor species. No recovery occurred between the next three mega-flows and the mass extinction was complete with the last phase-2 mega-flow at the KTB. The mass extinction was likely the consequence of rapid and massive volcanic CO2 and SO2 gas emissions, leading to high continental weathering rates, global warming, cooling, acid rains, ocean acidification and a carbon crisis in the marine environment.

Deccan volcanism phase-3 began in the early Danian near the C29R/C29n boundary correlative with the planktic foraminiferal zone P1a/P1b boundary and accounts for ~14% of the total volume of Deccan eruptions, including four of Earth’s longest and largest mega-flows. No major faunal changes are observed in the intertrappeans of zone P1b, which suggests that environmental conditions remained tolerable, volcanic eruptions were less intense and/or separated by longer time intervals thus preventing runaway effects. Alternatively, early Danian assemblages evolved in adaptation to high-stress conditions in the aftermath of the mass extinction and therefore survived phase-3 volcanism. Full marine biotic recovery did not occur until after Deccan phase-3. These data suggest that the catastrophic effects of phase-2 Deccan volcanism upon the Cretaceous planktic foraminifera were a function of both the rapid and massive volcanic eruptions and the highly specialized faunal assemblages prone to extinction in a changing environment. Data from the K-G Basin indicates that Deccan phase-2 alone could have caused the KTB mass extinction and that impacts may have had secondary effects.

URLhttp://link.springer.com/article/10.1007%2Fs12594-011-0107-3
DOI10.1007/s12594-011-0107-3
Short TitleJ Geol Soc India

Environmental effects of Deccan volcanism across the Cretaceous–Tertiary transition in Meghalaya, India

TitleEnvironmental effects of Deccan volcanism across the Cretaceous–Tertiary transition in Meghalaya, India
Publication TypeJournal Article
Year of Publication2011
AuthorsGertsch, B, Keller, G, Adatte, T, Garg, R, Prasad, V, Berner, Z, Fleitmann, D
JournalEarth and Planetary Science Letters
Volume310
Issue3-4
Pagination272 - 285
Date Published01/2011
ISSN0012821X
Abstract

The Um Sohryngkew section of Meghalaya, NE India, located 800–1000 km from the Deccan volcanic province, is one of the most complete Cretaceous–Tertiary boundary (KTB) transitions worldwide with all defining and supporting criteria present: mass extinction of planktic foraminifera, first appearance of Danian species, δ13C shift, Ir anomaly (12 ppb) and KTB red layer. The geochemical signature of the KTB layer indicates not only an extraterrestrial signal (Ni and all Platinum Group Elements (PGEs)) of a second impact that postdates Chicxulub, but also a significant component resulting from condensed sedimentation (P), redox fluctuations (As, Co, Fe, Pb, Zn, and to a lesser extent Ni and Cu) and volcanism. From the late Maastrichtian C29r into the early Danian, a humid climate prevailed (kaolinite: 40–60%, detrital minerals: 50–80%). During the latest Maastrichtian, periodic acid rains (carbonate dissolution; CIA index: 70–80) associated with pulsed Deccan eruptions and strong continental weathering resulted in mesotrophic waters. The resulting super-stressed environmental conditions led to the demise of nearly all planktic foraminiferal species and blooms (> 95%) of the disaster opportunist Guembelitria cretacea. These data reveal that detrimental marine conditions prevailed surrounding the Deccan volcanic province during the main phase of eruptions in C29r below the KTB. Ultimately these environmental conditions led to regionally early extinctions followed by global extinctions at the KTB.

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0012821X11004791
DOI10.1016/j.epsl.2011.08.015
Short TitleEarth and Planetary Science Letters

Foraminifera from the early Danian intertrappean beds in Rajahmundry quarries, Andhra Pradesh

TitleForaminifera from the early Danian intertrappean beds in Rajahmundry quarries, Andhra Pradesh
Publication TypeJournal Article
Year of Publication2010
AuthorsMalarkodi, N, Keller, G, Fayazudeen, PJ, Mallikarjuna, UB
JournalJournal of the Geological Society of India
Volume75
Issue6
Pagination851 - 863
Date PublishedJan-06-2010
ISSN0016-7622
Abstract

Intertrappean beds exposed between upper and lower traps of the Government and Sunnamrayalu quarries of Rajahmundry were analyzed based on benthic and planktic foraminifera, ostracodes and algae observed in thin sections. Planktic foraminifera indicate deposition occurred in the early Danian Parvularugoglobigerina eugubina (P1a) zone shortly after deposition of the lower trap flows. The most diverse planktic assemblages were deposited in limestones of the middle intertrappean interval and indicate an upper P1a age, or subzone P1a(2), as marked by the co-occurrence of P. eugubina, Globoconusa daubjergensis, Parasubbotina pseudobulloides and Subbotina triloculinoides. Reworked late Maastrichtian planktic foraminifera are common in a limestone interval and suggest erosion of uplifted Cretaceous sediments. Benthic foraminiferal assemblages indicate deposition occurred predominantly in shallow inner shelf to brackish environments. Similarly, ostracodes indicate variable environments ranging from inner neritic to brackish with fresh water influx, as also indicated by the presence of fresh water algae. These data confirm an overall deepening from restricted shallow marine to estuarine, lagoonal and finally open marine conditions followed by abrupt emersion and paleosoil deposition prior to the arrival of the upper trap flows at or near the base of C29n.

URLhttp://link.springer.com/article/10.1007%2Fs12594-010-0066-0
DOI10.1007/s12594-010-0066-0
Short TitleJ Geol Soc India

Deccan volcanism, the KT mass extinction and dinosaurs

TitleDeccan volcanism, the KT mass extinction and dinosaurs
Publication TypeJournal Article
Year of Publication2009
AuthorsKeller, G, Sahni, A, Bajpai, S
JournalJournal of Biosciences
Volume34
Issue5
Pagination709 - 728
Date PublishedJan-11-2009
ISSN0250-5991
Abstract

Recent advances in Deccan volcanic studies indicate three volcanic phases with the phase-1 at 67.5 Ma followed by a 2 m.y. period of quiescence. Phase-2 marks the main Deccan volcanic eruptions in Chron 29r near the end of the Maastrichtian and accounts for ∼80% of the entire 3500 m thick Deccan lava pile. At least four of the world’s longest lava flows spanning 1000 km across India and out into the Gulf of Bengal mark phase-2. The final phase-3 was smaller, coincided with the early Danian Chron 29n and also witnessed several of the longest lava flows.

The KT boundary and mass extinction was first discovered based on planktic foraminifera from shallow marine intertrappean sediments exposed in Rajahmundry quarries between the longest lava flows of the main volcanic phase-2 and smaller phase-3. At this locality early Danian (zone P1a) planktic foraminiferal assemblages directly overlie the top of phase-2 eruptions and indicate that the masse extinction coincided with the end of this volcanic phase. Planktic foraminiferal assemblages also mark the KT boundary in intertrappean sediments at Jhilmili, Chhindwara, where freshwater to estuarine conditions prevailed during the early Danian and indicate the presence of a marine seaway across India at KT time.

Dinosaur bones, nesting sites with complete eggs and abundant eggshells are known from central India surrounding the hypothesized seaway through the Narmada-Tapti rift zone. A Maastrichtian age is generally assigned to these dinosaur remains. Age control may now be improved based on marine microfossils from sequences deposited in the seaway and correlating these strata to nearby terrestrial sequences with dinosaur remains.

URLhttp://link.springer.com/article/10.1007%2Fs12038-009-0059-6
DOI10.1007/s12038-009-0059-6
Short TitleJ Biosci

Late Maastrichtian Volcanism in the Indian Ocean: Effects on Calcareous Nannofossils and Planktic Foraminifera

TitleLate Maastrichtian Volcanism in the Indian Ocean: Effects on Calcareous Nannofossils and Planktic Foraminifera
Publication TypeJournal Article
Year of Publication2009
AuthorsTantawy, AAAM, Keller, G, Pardo, A
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume284
Issue1-2
Pagination63 - 87
Date PublishedJan-12-2009
ISSN00310182
KeywordsBiotic effects, High stress environments, Indian Ocean Maastrichtian, Volcanism
Abstract

The biotic effects of volcanism have long been the unknown factors in creating biotic stress, and the contribution of the Deccan volcanism to the K–T mass extinction remains largely unknown. Detailed studies of the volcanic-rich sediments of Indian Ocean Ninetyeast Ridge Sites 216 and 217 and Wharton Basin Site 212 reveal that the biotic effects of late Maastrichtian volcanism on planktic foraminifera and calcareous nannofossils are locally as severe as those of the K–T mass extinction. The biotic expressions of these high stress environments are characterized by the Lilliput effect, which includes reduced diversity by eliminating most K-strategy species, and reduction in specimen size (dwarfing), frequently to less than half their normal adult size of both r-strategy and surviving K-strategy species. In planktic foraminifera, the most extreme biotic stress results are nearly monospecific assemblages dominated by the disaster opportunist Guembelitria, similar to the aftermath of the K–T mass extinction. The first stage of improving environmental conditions results in dominance of dwarfed low oxygen tolerant Heterohelix species and the presence of a few small r-strategy species (Hedbergella, Globigerinelloides). Calcareous nannofossil assemblages show similar biotic stress signals with the dominance of Micula decussata, the disaster opportunist, and size reduction in the mean length of subordinate r-strategy species particularly in Arkhangelskiella cymbiformis and Watznaueria barnesiae. These impoverished and dwarfed late Maastrichtian assemblages appear to be the direct consequences of mantle plume volcanism and associated environmental changes, including high nutrient influx leading to eutrophic and mesotrophic waters, low oxygen in the water column and decreased watermass stratification.

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018209003496
DOI10.1016/j.palaeo.2009.08.025
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

K–T transition in Deccan Traps of central India marks major marine Seaway across India

TitleK–T transition in Deccan Traps of central India marks major marine Seaway across India
Publication TypeJournal Article
Year of Publication2009
AuthorsKeller, G, Adatte, T, Bajpai, S, Mohabey, DM, Widdowson, M, Khosla, A, Sharma, R, Khosla, SC, Gertsch, B, Fleitmann, D
JournalEarth and Planetary Science Letters
Volume282
Issue1-4
Pagination10 - 23
Date PublishedJun-05-2011
ISSN0012821X
Abstract

Deccan intertrappean sediments in central India are generally considered as terrestrial deposits of Maastrichtian age, but the Cretaceous–Tertiary (K–T) position is still unknown. Here we report the discovery of the K–T transition, a marine incursion and environmental changes preserved within the intertrappean sediments at Jhilmili, Chhindwara District, Madhya Pradesh. Integrative biostratigraphic, sedimentologic, mineralogic and chemostratigraphic analyses reveal the basal Danian in the intertrappean sediments between lower and upper trap basalts that regionally correspond to C29r and the C29R/C29N transition, respectively. Intertrappean deposition occurred in predominantly terrestrial semi-humid to arid environments. But a short aquatic interval of fresh water ponds and lakes followed by shallow coastal marine conditions with brackish marine ostracods and early Danian zone P1a planktic foraminifera mark this interval very close to the K–T boundary. This marine incursion marks the existence of a nearby seaway, probably extending inland from the west through the Narmada and Tapti rift valleys. The Jhilmili results thus identify the K–T boundary near the end of the main phase of Deccan eruptions and indicate that a major seaway extended at least 800 km across India.

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0012821X09001034
DOI10.1016/j.epsl.2009.02.016
Short TitleEarth and Planetary Science Letters

Early Danian Planktic Foraminifera From Cretaceous-Tertiary Intertrappean Beds At Jhilmili, Chhindwara District, Madhya Pradesh, India

TitleEarly Danian Planktic Foraminifera From Cretaceous-Tertiary Intertrappean Beds At Jhilmili, Chhindwara District, Madhya Pradesh, India
Publication TypeJournal Article
Year of Publication2009
AuthorsKeller, G, Khosla, SC, Sharma, R, Khosla, A, Bajpai, S, Adatte, T
JournalThe Journal of Foraminiferal Research
Volume39
Issue1
Pagination40 - 55
Date PublishedJan-01-2009
ISSN0096-1191
Abstract

The main Deccan volcanic province erupted mainly in terrestrial to lacustrine environments of late Maastrichtian to early Paleocene age, and lack age diagnostic fossils to accurately place the Cretaceous-Tertiary (K-T) boundary. As a result, the precise position of the K-T event within the volcanic province has remained speculative, and no realistic assessment of the biotic consequences of Deccan volcanism at K-T time has been possible. Here, we report the discovery of early Danian Zone P1a planktic foraminifera within lacustrine to brackish-marine ostracod assemblages near Jhilmili, Chhindwara District, India. These foraminiferal assemblages identify the K-T boundary in intertrappean sediments bracketed by basalt traps that are regionally correlative with C29R (Ambenali Formation) and the C29R-C29N transition (Mahalabeshwar Formation). The Jhilmili sequence is thus correlative with the shallow-marine, intertrappean Zone P1a assemblage and C29R and C29N of the lower and upper basalt traps exposed in Rajahmundry quarries. The presence of planktic foraminifera in predominantly terrestrial intertrappean sediments some 800 km from the nearest ocean suggests the presence of a seaway along the Narmada and Tapti rift zones with Jhilmili located at the eastern margin.

URLhttp://jfr.geoscienceworld.org/cgi/doi/10.2113/gsjfr.39.1.40
DOI10.2113/gsjfr.39.1.40
Short TitleThe Journal of Foraminiferal Research

Cretaceous climate, volcanism, impacts, and biotic effects

TitleCretaceous climate, volcanism, impacts, and biotic effects
Publication TypeJournal Article
Year of Publication2008
AuthorsKeller, G
JournalCretaceous Research
Volume29
Issue5-6
Pagination754 - 771
Date PublishedJan-10-2008
ISSN01956671
KeywordsBiotic effects, Cretaceous Impacts, Mass extinctions, Volcanism
Abstract

Cretaceous volcanic activities (LIPs and CFBPs) appear to have had relatively minor biotic effects, at least at the generic level. Major biotic stress during the Cretaceous was associated with OAEs and related to nutrient availability largely from weathering, greenhouse warming, drowning of platform areas, and volcanism. The biotic effects of OAEs were often dramatic at the species level, causing the extinction of larger specialized and heavily calcified planktonic foraminifera (rotaliporid extinction) and nannoconids (nannoconid crises), the temporary disappearances of other larger species, and the rapid increase in r-selected small and thin-walled species, such as the low oxygen tolerant heterohelicids and radially elongated taxa among planktic foraminifera and thin walled nannofossils. Biotic diversity increased during cool climates, particularly during the late Campanian and Maastrichtian, reaching maximum diversity during the middle Maastrichtian. High biotic stress conditions began during greenhouse warming and Deccan volcanism about 400 ky before the K-T boundary; it reduced abundances of large specialized tropical planktic foraminiferal species and endangered their survival. By K-T time, renewed Deccan volcanism combined with a large impact probably triggered the demise of this already extinction prone species group.

Evidence from NE Mexico, Texas, and the Chicxulub crater itself indicates that this 170 km-diameter crater predates the K-T boundary by ∼300,000 years and caused no species extinctions. The Chicxulub impact, therefore, can no longer be considered a direct cause for the K-T mass extinction. However, the K-T mass extinction is closely associated with a global Ir anomaly, which is considered too large, too widespread, and too concentrated in a thin layer to have originated from volcanic activity, leaving another large impact as the most likely source. This suggests that a second still unknown larger impact may have triggered the K-T mass extinction.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0195667108000566
DOI10.1016/j.cretres.2008.05.030
Short TitleCretaceous Research

Main Deccan volcanism phase ends near the K–T boundary: Evidence from the Krishna–Godavari Basin, SE India

TitleMain Deccan volcanism phase ends near the K–T boundary: Evidence from the Krishna–Godavari Basin, SE India
Publication TypeJournal Article
Year of Publication2008
AuthorsKeller, G, Adatte, T, Gardin, S, Bartolini, A, Bajpai, S
JournalEarth and Planetary Science Letters
Volume268
Issue3-4
Start Page293
Date Published01/2008
ISSN0012821X
Keywordsdeccan volcanism, K–T mass extinction, paleoenvironment, Rajahmundry
Abstract

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.

URLhttp://www.sciencedirect.com/science/article/pii/S0012821X08000344
DOI10.1016/j.epsl.2008.01.015
Short TitleEarth and Planetary Science Letters

Biotic effects of late Maastrichtian mantle plume volcanism: implications for impacts and mass extinctions

TitleBiotic effects of late Maastrichtian mantle plume volcanism: implications for impacts and mass extinctions
Publication TypeJournal Article
Year of Publication2005
AuthorsKeller, G
JournalLithos
Volume79
Issue3-4
Pagination317 - 341
Date PublishedJan-02-2005
ISSN00244937
KeywordsBiotic effects, DSDP Site 216, Impacts, Late Maastrichtian, Planktic foraminifera Guembelitria, Volcanism
Abstract

During the late Maastrichtian, DSDP Site 216 on Ninetyeast Ridge, Indian Ocean, passed over a mantle plume leading to volcanic eruptions, islands built to sea level, and catastrophic environmental conditions for planktic and benthic foraminifera. The biotic effects were severe, including dwarfing of all benthic and planktic species, a 90% reduction in species diversity, exclusion of all ecological specialists, near-absence of ecological generalists, and dominance of the disaster opportunist Guembelitria alternating with low O2-tolerant species. These faunal characteristics are identical to those of the K–T boundary mass extinction, except that the fauna recovered after Site 216 passed beyond the influence of mantle plume volcanism about 500 kyr before the K–T boundary. Similar biotic effects have been observed in Madagascar, Israel, and Egypt. The direct correlation between mantle plume volcanism and biotic effects on Ninetyeast Ridge and the similarity to the K–T mass extinction, which is generally attributed to a large impact, reveal that impacts and volcanism can cause similar environmental catastrophes. This raises the inevitable question: Are mass extinctions caused by impacts or mantle plume volcanism? The unequivocal correlation between intense volcanism and high-stress assemblages necessitates a review of current impact and mass extinction theories.

 

 

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0024493704003111
DOI10.1016/j.lithos.2004.09.005
Short TitleLithos