ABSTRACTS

Highlights of the Latest Maastrichtian Grand Finale in the Western Tethys

TitleHighlights of the Latest Maastrichtian Grand Finale in the Western Tethys
Publication TypeConference Paper
Year of Publication2017
AuthorsPunekar, J, Keller, G, Adatte, T, Font, E
Conference NameGeological Society of America Annual Meeting
Date Published10/2017
PublisherGeological Society of America
Other NumbersSession No. 197-15, Abstract #305066
Abstract

The onset of Deccan main phase eruptions is estimated at the base of chron C29r, ~250 ky before the Cretaceous-Paleogene boundary (KTB or K-Pg or KPB). Lava mega-flows reaching eastern India stratigraphically underlie the KPB, standing testimony for peak volcanism preceding/straddling the KPB mass extinction. High-flux injections of thousands of gigatons of CO2 and SO2 into the atmosphere could have resulted in surface ocean acidification on variable timescales. Prolonged carbonate crisis is direct stress for marine calcifying planktic foraminifera, and may have played a critical role in their mass extinction. Initial multi-proxy evidence from Bidart (France) and Gamsbach (Austria) strongly support the acidification hypothesis. The current study aims at tracking the stratigraphic timing and nature of this event through the western Tethys Spanish KPB sections.

Carbonate dissolution intervals are recorded in the topmost ~50 cm at Agost and Caravaca (Spain), ~40 cm in Gamsbach and ~150 cm at Zumaiya (Spain). These correlate with the ~60 cm thick Deccan benchmark interval at Bidart (uppermost Maastrichtian zone CF1). Increased abundance (>40%) of dwarfed Guembelitria (<63μm fraction) in the suspect interval at Bidart, Zumaya and Caravaca associated with pulsed mercury peaks (>20 ppb, background values are <0.1 ppb) suggest high faunal stress and ongoing volcanism. The most expanded known KPB transition at Elles (Tunisia) yields a tentative event onset age of ~ 50 ky pre-KPB. The correlative intertrappean sediments between lava mega-flows in the Krishna-Godavari basin (eastern India) record acute carbonate dissolution and rapid diversity decline in planktic foraminifera. The new findings lend strength to a link between intensified Deccan volcanism and the faunal stress build up in the final ~50 ky, leading up to the KPB mass extinction.

URLhttps://gsa.confex.com/gsa/2017AM/webprogram/Paper305066.html
DOI10.1130/abs/2017am-305066

Timing and tempo of Deccan volcanism: evidence from mercury anomalies

TitleTiming and tempo of Deccan volcanism: evidence from mercury anomalies
Publication TypeConference Proceedings
Year of Conference2017
AuthorsAdatte, T, Font, E, A. Bitchong, M, Keller, G, Schoene, B, Samperton, K, Khadri, S
Conference NameEGU General Assembly Conference Abstracts
Date Published04/2017
Publisher19th EGU General Assembly
Conference LocationVienna, Austria
Other Numbersp.7709
Abstract

Mercury is a very toxic element, with a long residence time (1-2 years) and wide distribution by aerosols. Volcanic emissions and coal combustion are the two main natural sources of mercury. Several studies [1-4] evaluated the relationship between Hg anomalies in sediments and LIP activity across mass extinction horizons. The bulk (80%) of Deccan Trap eruptions occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology reveals the onset of this main eruption phase 250 ky before the Cretaceous-Tertiary (KT) mass extinction and continued into the early Danian suggesting a cause-and-effect relationship [5]. In a related study we investigate the mercury (Hg) contents of sections in France (Bidart), Spain (Zumaya), Denmark (Nye Klov), Austria (Gams), Italy (Gubbio), Tunisia (Elles, El Kef), Egypt (Sinai), India (Megalaya), Texas USA (Brazos River) and Mexico (La Parida). In all sections, results show Hg concentrations are more than 2 orders of magnitude greater during the last 100ky of the Maastrichtian up to the early Danian P1a zone (first 380 Ky of the Paleocene). These Hg anomalies are correlative with the main Deccan eruption phase. Hg anomalies generally show no correlation with clay or total organic carbon contents, suggesting that the mercury enrichments resulted from higher input of atmospheric Hg species into the marine realm, rather than organic matter scavenging and/or increased run-off. At Gams, Bidart and Elles, Hg anomalies correlate with high shell fragmentation and dissolution effects in planktic foraminifera indicating that paleoenvironmental and paleoclimate changes drastically affected marine biodiversity. These observations provide further support that Deccan volcanism played a key role in increasing atmospheric CO2 and SO2 levels that resulted in global warming and acidified oceans, increasing biotic stress that predisposed faunas to eventual extinction at the KTB.

URLhttp://adsabs.harvard.edu/abs/2017EGUGA..19.7709A

Mercury Stratigraphy of Deccan Trap Volcanism in Marine Sediments Linked to Climate Change, Biotic Turnover, End-Cretaceous Mass Extincetion and Delayed Recovery

TitleMercury Stratigraphy of Deccan Trap Volcanism in Marine Sediments Linked to Climate Change, Biotic Turnover, End-Cretaceous Mass Extincetion and Delayed Recovery
Publication TypeConference Paper
Year of Publication2017
AuthorsKeller, G, Adatte, andThierry, Spangenberg, JE, Mateo, P, Punekar, J, Schoene, B, Samperton, KMichael, Eddy, MPatterson
Conference NameGeological Society of America Annual Meeting
Date Published10/2017
PublisherGeological Society of America
Conference LocationSeattle, Washington
Other NumbersSession No. 197-13, Abstract #303559
Abstract

Mercury (Hg) as indicator of large-scale volcanism in marine sediments provides new insights into relative timing between biological and environmental changes, mass extinctions and delayed recovery. We analyzed Hg concentrations linked to Deccan volcanism, TOC, δ13C, δ18O and faunal changes for C29r that spans 250 ky below the Cretaceous-Paleogene boundary (KPB) at Elles, Tunisia. The sediment accumulation rate is 8.6 cm/ky making this the most complete and expanded sequence known worldwide. Sample analyses at 10 cm intervals yield a data point every 1160 years. Relatively high Hg/TOC ratios are first recorded 1.6 m above the C30n/C29r boundary (base zone CF2). Sustained high pulsed Hg/TOC ratios lasted from 200 to 135 ky pre-KPB (calculated from sedimentation rates), correlative with global warming and decreased δ13C values. Variable Hg/TOC ratios and cooling between 133 and 90 ky was followed by low ratios, warming and decreased δ13C between 90-56 ky. Fluctuating Hg/TOC, cooling and increased δ13C prevailed between 55 to 18 ky. Maximum Hg/TOC ratios and rapid warming during the last 18 ky culminate in the KPB mass extinction. Lower frequency Hg/TOC ratios continue through the early Danian C29r and implicate Deccan volcanism also in the delayed recovery after the mass extinction.

Faunal turnovers mirror Hg/TOC ratios, δ18O and δ13C trends. Analyses of three size fractions (38-63 mm, >63 mm, >150 mm) reveal strong dwarfing and high-stress environmental conditions. Dwarfed (38-63 mm) disaster opportunist Guembelitria cretacea are common throughout C29r but reached maximum stress (85%) during the last 8 ky prior to the mass extinction. Small, low oxygen tolerant biserial species (38-63 mm, >63 mm) dominated C29r at times of increased biotic stress and climate warming (C29r up to 90 ky) suggesting disoxic conditions. Larger, more complex species are generally rare. The mass extinction occurred during the last 8-10 ky, a time of maximum Hg/TOC ratios linked to Deccan volcanism, rapid climate warming and ocean acidification.

What role, if any, the Chicxulub impact played in this mass extinction is still controversial. The common assumption that this impact occurred precisely at the KPB is contradicted by evidence of primary impact spherule deposition ~100 ky prior to the mass extinction in Mexico.

URLhttps://gsa.confex.com/gsa/2017AM/webprogram/Paper303559.html
DOI10.1130/abs/2017am-303559

Toward a High-Resolution Age Model for the Deccan Traps by U-PB Zircon Geochronology

TitleToward a High-Resolution Age Model for the Deccan Traps by U-PB Zircon Geochronology
Publication TypeConference Paper
Year of Publication2017
AuthorsSchoene, B, Samperton, KMichael, Eddy, MP, Keller, G, Adatte, T, Khadri, SFR
Conference NameGeological Society of America Annual Meeting
Date Published10/2017
PublisherGeological Society of America
Conference LocationSeattle, Washington
Other NumbersSession No. 197-9, Abstract #305419
Abstract

Both the Chicxulub bolide impact and the Deccan Traps large igneous province have been implicated as contributing to the end-Cretaceous mass extinction. However, linking these events to the stratigraphic record of biotic and climatic change around the extinction, and assessing their potential effects, requires precise temporal constraints.. To better constrain the timing and tempo of Deccan Traps volcanism, we apply CA-TIMS U-Pb zircon geochronology, which can yield eruption ages at the ±20 kyr level.
Because basalt typically does not crystallize zircon, we have focused our sampling efforts on paleosol horizons between basalt flows (locally termed “redboles”) that sometimes contain small amounts of zircon-bearing volcanic ash. Of >150 such samples collected over three field excursions, ~25 redboles spanning >90% of Deccan Traps stratigraphy have yielded zircon. We combine age data with stratigraphic constraints and zircon geochemistry to inform best estimates for each sample’s eruption date, with uncertainties typically <±50 kyr (2σ). These data are used to test existing regional stratigraphic correlations and build an age model for the Deccan eruptions.

Our results are consistent with recently published U-Pb and 40Ar/39Ar geochronological data that demonstrate the majority of Deccan Traps basalt erupted in ~700 kyr, beginning near the C30n/C29r magnetic reversal, ~250 kyr before the main extinction event. We find that while our data can be used to resolve the tempo and duration of magmatic activity from individual stratigraphic sections, uncertainties in stratigraphic correlation present a challenge to quantifying eruption rates. Therefore, despite the extensive number of excellent geologic studies thus far undertaken in the Deccan Traps, additional mapping, stratigraphy, geochemistry, and geochronology may be required before calculating robust volumetric eruptions rates is tenable. Such data are essential to test models that address the effect of Deccan eruptions on the biosphere and carbon cycle on 100 kyr timescales, and to test proposed linkages between the Deccan Traps, the end-Cretaceous extinction, and Chicxulub impact.

 

 

URLhttps://gsa.confex.com/gsa/2017AM/webprogram/Paper305419.html
DOI10.1130/abs/2017am-305419

Evaluating Carbon and Climate Sensitivities of the NOAA/GFDL Earth System Model ESM2Mb to Forcing Perturbations during the Paleocene-Eocene Thermal Maximum

TitleEvaluating Carbon and Climate Sensitivities of the NOAA/GFDL Earth System Model ESM2Mb to Forcing Perturbations during the Paleocene-Eocene Thermal Maximum
Publication TypeConference Paper
Year of Publication2017
AuthorsTandy, H, Shevliakova, E, Keller, G
Conference NameAmerican Geophysical Union Fall Meeting
Date Published12/2017
PublisherAmerican Geophysical Union
Conference LocationNew Orleans, LA
URLhttps://agu.confex.com/agu/fm17/preliminaryview.cgi/Paper291998.html

Environmental Changes Associated With Deccan Volcanism: evidences from the red bole record

TitleEnvironmental Changes Associated With Deccan Volcanism: evidences from the red bole record
Publication TypeConference Paper
Year of Publication2017
AuthorsNikhil, S, Valentin, S, Thierry, A, Gerta, K, Eric, F, Blair, S, Kyle, S, Syed, K
Conference NameEGU General Assembly Conference Abstracts
Publisher19th EGU General Assembly
Conference LocationVienna, Austria
Other Numbersp.7905
Abstract

Recent studies indicate that the bulk (80%) of Deccan trap eruptions occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology shows that the main phase-2 began 250 ky before the Cretaceous-Tertiary (KT) mass extinction and continued into the early Danian suggesting a cause-and-effect relationship. Closer to the eruption center, the lava flows are generally separated by red weathered horizons known as red boles that mark quiescent periods between basalt flows. A typical red bole begins with the fresh underlying basalt and evolves into weathered basalt, then, a layer of basalt in a rounded shape called 'bole' surrounded by clays at the top, which is overlain by the next lava flow. Red boles have increasingly attracted the attention of researchers to understand the climatic and paleoenvironmental impact of Continental Flood Basalts (CFB). Recent advances in U-Pb dating of Deccan lava flows, studies of weathering patterns and paleoclimatic information gained from multiproxy analyses of red bole beds (e.g., lithology, mineralogy, geochemistry) yield crucial evidence of environmental changes triggered by volcanic activity. Red boles consist mainly of red silty clays characterized by concentrations of immobile elements such as Al and Fe3+ ions that are typical of paleo-laterites, which probably developed during the short periods of weathering between eruptions. Clay minerals consist mostly of smectite suggesting semi-arid monsoonal conditions. At least 30 thick red bole layers are present in C29r below the KT boundary between lava flows of phase-2 that erupted over a time span of about 250 ky. The short duration exposures of these red boles are reflected in the mineralogical and geochemical data that indicate rapid weathering (high CIA) linked to increasing acid rains. ∂D and ∂18O measured on smectite clays from the red boles approximate the meteoric water composition that prevailed during Deccan eruptions. Isotopic data from red boles deposited through the main phase-2 suggest significant and rapid changes in rainfall intensity and/or altitude linked to the accumulation of a 3100m thick basalt pile that erupted over a short period of time.

URLhttp://adsabs.harvard.edu/abs/2017EGUGA..19.7905N

Deciphering the magnetic and mineralogical record of the Deccan Traps at the Cretaceous-Paleogene boundary of the Zumaia section, Basque-Cantabric basin (Spain)

TitleDeciphering the magnetic and mineralogical record of the Deccan Traps at the Cretaceous-Paleogene boundary of the Zumaia section, Basque-Cantabric basin (Spain)
Publication TypeConference Paper
Year of Publication2017
AuthorsFont, E, Adatte, T, Andrade, M, Keller, G, A. Bitchong, M, Carvallo, C, Ferreira, J, Diogo, Z, Mirão, J
Conference NameEGU General Assembly Conference Abstracts
Publisher19th EGU General Assembly
Conference LocationVienna, Austria
Other Numbersp.9160
Abstract

The Deccan Traps Magmatic Province coincides with the Cretaceous-Paleogene (KPg) boundary and probably contributed to the associated mass extinctions by inducing rapid and abrupt climate changes, including continental and superficial seawater acidification. However, how such environmental acidification is expressed in the marine sedimentary record is still poorly constrained. Recent environmental magnetic studies of the Bidart (France) and Gubbio (Italy) sections proposed new benchmarks to identify the Deccan Traps fingerprint in the marine sedimentary record, namely anomalous concentration in mercury, presence of akagenéite (a Cl-rich oxy-hydroxide forming in hyper-chlorinated and acid conditions) and the loss of detrital and biogenic magnetite by acid reductive dissolution. Here we test this scenario on the Zumaia section, Spain, a reference KPg section cropping out in the Basque-Cantabric basin. Our results confirm the presence of an iron-depleted interval located just below the KPg boundary, similarly to Bidart and Gubbio, and which contains significant amounts of akaganéite grains as well as high content in mercury. These results consolidate the use of the previously cited benchmarks to identify environmental and climate changes induced by the Deccan volcanism. It also suggests that the main eruptive Deccan phase began just before the KPg extinction, reinforcing its contribution in the KPg mass extinction. Publication supported by FCT- project UID/GEO/50019/2013 - Instituto Dom Luiz

Continental vegetation and climate dynamics during Oceanic Anoxic Event 2

TitleContinental vegetation and climate dynamics during Oceanic Anoxic Event 2
Publication TypeConference Paper
Year of Publication2017
AuthorsHeimhofer, U, Wucherpfennig, N, Adatte, T, Schouten, S, Schneebeli-Hermann, E, Gardin, S, Keller, G, Kujau, A
Conference Name10th ISC – International Symposium on the Cretaceous
PublisherBerichte der Geologischen Bundesanstalt
Conference LocationVienna, Austria
Other NumbersISSN 107-8880
Abstract

The Cenomanian-Turonian boundary witnessed major perturbations in global biogeochemical cycling, oceanography and climate expressed in the widespread deposition of organic-rich marine shales (OAE2) and a pronounced positive carbon isotope excursion (CIE). Despite the global significance of this event, information on the dynamics of continental ecosystems during OAE2 is still lacking. Given the outstanding warm seasurface temperatures (SSTs) reconstructed from proxy data for the OAE2 interval, the composition of terrestrial biomes must have responded to the inferred climatic changes. Here we present palynological and organic-geochemical data from a stratigraphically wellconstrained marine succession from the Southern Provence Basin (SPB) located in the western Tethys domain. New biostratigraphic results (calcareous nannofossils, planktonic foraminifera) coupled with carbon isotope stratigraphy show that the interval corresponding to the OAE2 and associated CIE is represented by a ~150 m thick section composed of marls with few limestone intercalations. TEX86 data indicate very warm SSTs of up to 33°C, which is in line with previous mid-latitude temperature records. An interval with lower TEX86- derived temperature estimates is paralleled by a trough-shaped decline in carbon-isotopes and tentatively correlated with the so-called Plenus Cold Event, a phase of distinct cooling in the early phase of OAE2. The spore-pollen assemblage is dominated by non-saccate gymnosperm (Inaperturopollenites, Araucariacites, Classopollis) and angiosperm pollen(mainly representatives of the Normapolles group incl. Atlantopollis and Complexiopollis), with pteridophyte spores being diverse but quantitatively less important. With stratigraphic height, the spore-pollen assemblage shows distinct changes in frequency distribution patterns including a pronounced increase in Inaperturopollenites and Classpollis. In contrast, the interval assigned to the Plenus Cold Event is characterized by a distinct rise in the angiosperm pollen Atlantopollis microreticulatus, reaching up to 16.4 % of the total palynoflora. In summary, the integrated palynological and geochemical dataset from the SPB documents the dynamics of mid-latitude vegetation during a phase of outstanding global warmth during OAE2. Despite the exceptional temperatures, a diverse and rich flora occupying various habitats in the hinterland of the SPB can be observed. Fluctuations in spore-pollen frequency distribution are considered to reflect significant climatic changes in the course of OAE2 controlled ultimately by the interplay of large-scale magmatic activity and enhanced organic carbon burial.  PDF

URLhttps://opac.geologie.ac.at/wwwopacx/wwwopac.ashx?command=getcontent&server=images&value=BR0120_110.pdf

The Role of Volcanism (North Atlantic Igneous Province) in the PETM Events Revealed by Mercury Anomalies

TitleThe Role of Volcanism (North Atlantic Igneous Province) in the PETM Events Revealed by Mercury Anomalies
Publication TypeConference Paper
Year of Publication2017
AuthorsKhozyem, H, Adatte, T, Bitchong, AMbabi, Mohamed, A, Keller, G
Conference NameGeological Society of America Annual Meeting
Date Published10/2017
PublisherGeological Society of America
Conference LocationSeattle, Washington
Other NumbersSession No. 228-5, Abstract #302893
Abstract

The Paleocene-Eocene Thermal Maximum (PETM, ≈55.8±0.2 Ma) is marked by a global change in carbon cycle and rapid warming. Climate warming persisted for several tens of thousands of years and resulted in rapid diversification in terrestrial mammals and marine planktic foraminifera.

Deep-water benthic foraminifera suffered a mass extinction (≈40% species) but no significant extinctions occurred shallow shelf environments. Benthic extinctions are commonly explained as the effects of the initial stage of climate warming due to North Atlantic Volcanic Province volcanism (NAVP), which triggered methane release from ocean sediments causing global warming and ocean acidification. But the relationship between NAPV and the PETM events are till now not clearly demonstrated.

Several studies demonstrated the relationship between Hg anomalies in sediments and LIP activity associated with mass extinctions. Mercury (Hg) content of several sections located in different sedimentary environments (deep bathyal: Zumaya, Trabakua, N-Spain and outer shelf: Dababiya GSSP, Duwi, Wadi Nukhul, Egypt, terrestrial: Esplugafreda) were determined. At Zumaya the PETM is marked by a red clayey and marly interval poor in organic matter and coincident with a pronounced δ13C negative shift. A comparable clay interval with low TOC content is also present in the Dababyia section in the lower part of the negative δ13C shift, whereas the upper part of is enriched in TOC, reflecting increased productivity. The Esplugafreda section located in South Central Pyrenees shows an excellent terrestrial record of the early Eocene warm events. High-resolution δ13C and δ18O analyses of two types of calcareous paleosoil nodules reveal two distinct negative excursions a Pre-Onset Excursion (POE) and the Paleocene Eocene Thermal Maximum (PETM), both characterized by significant Hg enrichments.

This Hg enrichment is not linked to clays or total organic carbon contents, and suggests that Hg anomaly resulted from higher atmospheric Hg input into the marine realm, rather than organic matter scavenging and/or increased run-off.

The presence of several peaks of mercury coincident with both POE and PETM intervals supports the role of volcanism (North Atlantic Igneous Province) to initiate the concomitant warming and sea-level rise characterizing the POE and PETM.

URLhttps://gsa.confex.com/gsa/2017AM/webprogram/Paper302839.html
DOI10.1130/abs/2017am-302839

Near Coincidence of Maximum Deccan Volcanism with the Cretaceous-Paleogene Boundary Revealed by Mercury Anomalies

TitleNear Coincidence of Maximum Deccan Volcanism with the Cretaceous-Paleogene Boundary Revealed by Mercury Anomalies
Publication TypeConference Paper
Year of Publication2017
AuthorsAdatte, T, Keller, andGerta, Font, E, Bitchong, AMbabi, Schoene, B, Samperton, K, Eddy, MP
Conference NameGeological Society of America Annual Meeting
Date Published10/2017
PublisherGeological Society of America
Conference LocationSeattle, Washington
Other NumbersSession No. 197-2, Abstract #302876
Abstract

Mercury is a very toxic element, with a long residence time (1-2 years) and wide distribution by aerosols. Several studies evaluated the relationship between Hg anomalies in sediments and LIP activity across mass extinction horizons. The bulk (80%) of Deccan Trap eruptions occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology reveals the onset of this main eruption phase 250 ky before the Cretaceous-Tertiary (KT) mass extinction and continued into the early Danian suggesting a cause-and-effect relationship. We investigate the mercury (Hg) contents of sections in France (Bidart), Spain (Zumaya), Denmark (Nye Klov), Austria (Gams), Italy (Gubbio), Tunisia (Elles, El Kef), Egypt (Wadi Nukhul, Sinai, Duwi, Eastern Desert), Israel (Negev), India (Megalaya), Texas USA (Brazos River) and NE Mexico (El Penon, La Parida). In all sections, results show Hg concentrations are more than 2 orders of magnitude greater during the last 100ky of the Maastrichtian up to the early Danian P1a zone (first 380 Ky of the Paleocene). These Hg anomalies are correlative with the main Deccan eruption phase. Hg anomalies generally show no correlation with clay or total organic carbon contents, suggesting that the mercury enrichments resulted from higher input of atmospheric Hg species into the marine realm, rather than organic matter scavenging and/or increased run-off. At Gams, Bidart and Elles, Hg anomalies correlate with high shell fragmentation and dissolution effects in planktic foraminifera indicating that paleoenvironmental and paleoclimate changes drastically affected marine biodiversity. Hg isotope data from Bidart support a direct fallout from volcanic aerosols. PGEs data from Mishor Rotem (Israel) from the KPg layer and two uppermost Maastritchian red clay layers provide some important clues about the Hg deposited in the KPg layer, which appears to be more linked to volcanism than impact, suggesting a major pulse of Deccan activity just before and at the KPg.

These observations provide further support that Deccan volcanism played a key role in increasing atmospheric CO2 and SO2 levels that resulted in global warming and acidified oceans, increasing biotic stress that predisposed faunas to eventual extinction at the KPg.

URLhttps://gsa.confex.com/gsa/2017AM/webprogram/Paper302876.html
DOI10.1130/abs/2017am-302876

Delayed faunal recovery in the aftermath of the end-Cretaceous mass extinction: Links to Deccan volcanism and Dan-C2 warming?

TitleDelayed faunal recovery in the aftermath of the end-Cretaceous mass extinction: Links to Deccan volcanism and Dan-C2 warming?
Publication TypeConference Paper
Year of Publication2017
AuthorsMateo, P, Keller, andGerta, Tandy, H, Adatte, T, Khozyem, H
Conference NameGeological Society of America Annual Meeting
Date Published10/2017
PublisherGeological Society of America
Conference LocationSeattle, Washington
Other NumbersSession No. 197-14, Abstract #303185
Abstract

Persistent high stress environmental conditions and over 1 Myr delayed recovery in planktic foraminiferal communities in the aftermath of the end-Cretaceous mass extinction have been linked to continued Deccan volcanism activity in India. In addition, the Dan-C2 hyperthermal event in the early Danian (planktic foraminiferal zone P1b) has been associated to the last pulse of Deccan volcanism. We test these potential cause-and-effect relationships at ODP Site 1049 in the western North Atlantic based on high-resolution quantitative planktonic foraminiferal biostratigraphy, oxygen and carbon stable isotopes, bulk-rock mineralogy, major element geochemistry, and mercury anomalies as proxy for volcanism.

Results show that a double spike in mercury concentrations is recorded in zone P1b, C29n, coeval with increased relative abundance of opportunist species, a 2 ºC warming, and decreased productivity, marking climate instability and biotic stress directly linked to the last phase of Deccan volcanism, thus supporting previous findings of volcanically-induced high stress conditions during this time. The onset of planktic foraminiferal recovery is recorded in zone P1c(1) after the last phase of Deccan volcanism ended also supporting previous claims that the delayed recovery was due to Deccan volcanism. But results also show that the Dan-C2 event occurred in zone P1c(1), well after the last phase of Deccan volcanism ended, and caused no faunal changes in planktic foraminiferal assemblages. This climate event appears to be the result of increased shallow water input (commonly observed in continental slope locations in the North Atlantic) rather than a hyperthermal event related to Deccan volcanism. Other isotopic anomalies observed in the South Atlantic, Italy and Ukraine, initially interpreted as the Dan-C2 event and claimed as evidence of its global extent, actually occurred during the early Danian C29r (zone P1a) phase of Deccan volcanism. High-resolution studies are still needed to determine the precise timing of these isotopic excursions and their links, if any, to Deccan volcanism.

 

 

URLhttps://gsa.confex.com/gsa/2017AM/webprogram/Paper303185.html
DOI10.1130/abs/2017am-303185

Age, Biostratigraphy, Geochemistry, and Mineralogy of Chicxulub Impact Spherules on Gorgonilla Island, Colombia

TitleAge, Biostratigraphy, Geochemistry, and Mineralogy of Chicxulub Impact Spherules on Gorgonilla Island, Colombia
Publication TypeConference Paper
Year of Publication2016
AuthorsMateo, P, Keller, G, Adatte, T, Bitchong, A, Spangenberg, J, Vennemann, T, Heizler, M, Hodges, K, McDonald, C, Hollis, C, Stinnesbeck, W
PublisherGeological Society of America
Conference LocationDenver, Colorado
Abstract

The age of the Chicxulub impact is still controversial. Impact spherules found at or near the Cretaceous-Paleogene boundary (KPB) in the North Atlantic, Caribbean, Belize and Guatemala are reworked in early Danian sediments above a KP hiatus [1-3]. But, in NE Mexico and Texas where impact spherules are beyond erosion by the Gulf Stream, they are found in late Maastrichtian sediments with the primary spherule layer predating the KPB by ~100 ky [4,5]. Recent discovery of pristine Chicxulub impact glass spherules on Gorgonilla Island, Colombia [6], and re-sampling of the section sheds new light on this controversy. Sediments consist of radiolarian-rich marls alternating with volcanic-rich turbidites depleted in calcite. Three closely spaced ~2 cm-thick spherule beds, two discontinuously present, overlie a late Maastrichtian erosion surface and have a similar mineralogical composition as the turbidites, suggesting spherule re-deposition marked by decreasing grain size and repetition of beds due to slumping. Spherule beds contain reworked Maastrichtian species and clay clasts with early Danian planktic foraminifera typical of zone P1a(2) about 150-200 ky after the KPB indicating re-deposition during the early Danian. Study of radiolaria is in progress. δ13Corg.carb values show no negative shift near the spherule bed, confirming a KPB hiatus, as also indicated by absence of significant Ni and Co enrichments. δ18O by laser ablation of spherules have a wide range of values (8.5 to 10.4‰) typical of andesitic-dacitic (~8‰) and rhyolitic glass (9 to 10‰), suggesting melt contaminated with sedimentary material. While these analyses confirm an impact origin, spherules with higher SiO2content also have higher d18O values, indicating crystal fractionation processes or assimilation of sedimentary material. Preliminary 40Ar/39Ar dating of Gorgonilla impact spherules is currently underway at two laboratories.

URLhttps://gsa.confex.com/gsa/2016AM/webprogram/Paper282848.html
DOI10.1130/abs/2016am-282848

40 AR / 39 AR Dating of Chicxulub Impact Spherules from Isla Gorgonilla, Columbia

Title40 AR / 39 AR Dating of Chicxulub Impact Spherules from Isla Gorgonilla, Columbia
Publication TypeConference Paper
Year of Publication2016
AuthorsMcDonald, CS, Heizler, M, Hodges, K, Keller, G, Adatte, T
Conference NameGeological Society of America Annual Meeting
PublisherGeological Society of America
Conference LocationDenver, Colorado
Other NumbersSession No. 106
Abstract

Glass spherules are a common occurrence around the Cretaceous-Paleogene (KPG) boundary in the stratigraphic record throughout the Caribbean and North Atlantic and are widely thought to represent tektites produced by the Chicxulub impact [1,2]. A new example, which contains some of the largest individual spherules yet found (typically 0.5–1.5 mm in diameter), was recently discovered on Isla Gorgonilla, off the Pacific coast of Colombia [3]. Here, the tektites occur in 2-3 discontinuous layers, within alternating sequences of mudstones and turbidites, and show varying degrees of minor, post-depositional alteration. Based on fossil assemblages, the ages of the tektite layers are thought to closely approximate the KPG, but the size and composition of the spherules invites 40Ar/39Ar dating to constrain their ages more precisely. Here we present the results of preliminary laser step-heating experiments on roughly 30 individual spherules undertaken at both Arizona State University and the New Mexico Institute of Mining and Technology. Step-heating experiments at both facilities yield similar release spectra that are characterized by young dates for low-temperature steps, that climb to either formally defined plateaus or near-plateaus for the bulk of the gas released at higher temperatures. We presently infer that the young, low-temperature dates reflect variable amounts of post-depositional alteration and consequent 40Ar loss. Such alteration also may be responsible for the fact that the plateau dates from both laboratories are slightly over dispersed, that is, slightly too variable to be solely explained by analytical imprecision alone. At present, while we cannot infer a highly precise age for the impact event (or events) responsible for these tektites, the developing dataset indicates an age within no more than a few hundred thousand years of current estimates for the KPG boundary. The preliminary data are encouraging and indicate that further work may hold valuable constraints on the timing of Chicxulub impact and its temporal relation to the biostratigraphic record.

URLhttps://gsa.confex.com/gsa/2016AM/webprogram/Paper286177.html
DOI10.1130/abs/2016am-286177

Spatial and Temporal Constraints on the End-Maastrichtian Ocean Acidification Related to Deccan Volcanism

TitleSpatial and Temporal Constraints on the End-Maastrichtian Ocean Acidification Related to Deccan Volcanism
Publication TypeConference Paper
Year of Publication2016
AuthorsPunekar, J, Keller, G, Adatte, T, Font, E
Conference NameGeological Society of America Annual Meeting
Date Published01/2016
PublisherGeological Society of America
Conference LocationDenver, Colorado
Other NumbersSession No. 106
Abstract

Preliminary results show poor planktic foraminifer test preservation in the top ~1 m (zone CF1) at Agost, correlative with high-stress conditions preceding the mass extinction horizon at Bidart, Gamsbach and Elles (Tunisia). Correlative zone CF1 sediments in the eastern Tethys (Egypt, Israel) show inverse correlation between carbonate preservation and blooms of the disaster opportunist Guembelitria that links ocean acidification with high-stress conditions in planktic foraminifera. Close to the volcanic source in India significantly stronger carbonate dissolution effects are recorded in Meghalaya [3] to the northeast and in intertrappean sediments between the longest lava flows of the Deccan volcanic province that ended with the mass extinction [4]. Global documentation of Deccan volcanism-related proxies and environmental effects preceding the KTB mass extinction is now possible and brings much needed clarity and improved understanding of the catastrophic effects of Large Igneous Province (LIP) volcanic eruptions during four of the five big mass extinctions in Earth’s history.

URLhttps://gsa.confex.com/gsa/2016AM/webprogram/Session40122.html
DOI10.1130/abs/2016am-283735

Accelerating Deccan Eruptions and Runaway Climate Change

TitleAccelerating Deccan Eruptions and Runaway Climate Change
Publication TypeConference Paper
Year of Publication2016
AuthorsKeller, G, Adatte, T, Punekar, J, Mateo, P, Spangenberg, J, Schoene, B, Samperton, K, Khadri, SFR
Conference NameGeological Society of America Annual Meeting
Date Published09/2016
PublisherGeological Society of America
Conference LocationDenver, Colorado
Other NumbersSession No. 106-7
Abstract

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].

URLhttps://gsa.confex.com/gsa/2016AM/webprogram/Paper283710.html
DOI10.1130/abs/2016am-283710

Timing and Tempo of Deccan Volcanism Revealed by Mercury Anomalies

TitleTiming and Tempo of Deccan Volcanism Revealed by Mercury Anomalies
Publication TypeConference Paper
Year of Publication2016
AuthorsAdatte, T, Font, E, Mbabi-Bitchong, A, Keller, G, Schoene, B, Samperton, KM, Khadri, SFR
Conference NameGeological Society of America Annual Meeting
Date Published09/2016
PublisherGeological Society of America
Conference LocationDenver, Colorado
Other NumbersSession No. 106-6
Abstract

Mercury is a very toxic element, with a long residence time (1-2 years) and wide distribution by aerosols. Volcanic emissions and coal combustion are the two main natural sources of mercury. Several studies [1-4] evaluated the relationship between Hg anomalies in sediments and LIP activity across mass extinction horizons. The bulk (80%) of Deccan Trap eruptions occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology reveals the onset of this main eruption phase 250 ky before the Cretaceous-Tertiary (KT) mass extinction and continued into the early Danian suggesting a cause-and-effect relationship [5]. In a related study we investigate the mercury (Hg) contents of sections in France (Bidart), Spain (Zumaya), Denmark (Nye Klov), Austria (Gams), Italy (Gubbio), Tunisia (Elles, El Kef), Egypt (Sinai), India (Megalaya), Texas USA (Brazos River) and Mexico (La Parida). In all sections, results show Hg concentrations are more than 2 orders of magnitude greater during the last 100ky of the Maastrichtian up to the early Danian P1a zone (first 380 Ky of the Paleocene). These Hg anomalies are correlative with the main Deccan eruption phase. Hg anomalies generally show no correlation with clay or total organic carbon contents, suggesting that the mercury enrichments resulted from higher input of atmospheric Hg species into the marine realm, rather than organic matter scavenging and/or increased run-off. At Gams, Bidart and Elles, Hg anomalies correlate with high shell fragmentation and dissolution effects in planktic foraminifera indicating that paleoenvironmental and paleoclimate changes drastically affected marine biodiversity. These observations provide further support that Deccan volcanism played a key role in increasing atmospheric CO2 and SO2 levels that resulted in global warming and acidified oceans, increasing biotic stress that predisposed faunas to eventual extinction at the KTB.

URLhttps://gsa.confex.com/gsa/2016AM/webprogram/Paper285123.html
DOI10.1130/abs/2016am-285123

Paleocene-Eocene Thermal Maximum Triggered by Volcanism Evidence from Mercury Anomalies

TitlePaleocene-Eocene Thermal Maximum Triggered by Volcanism Evidence from Mercury Anomalies
Publication TypeConference Paper
Year of Publication2016
AuthorsKhozyem, H, Adatte, T, Bitchong, AMbabi, Chevalier, Y, Keller, G
Conference NameGeological Society of America Annual Meeting
Date Published09/2016
PublisherGeological Society of America
Conference LocationDenver, Colorado
Other NumbersSession No. 106-2
Abstract

The Paleocene-Eocene Thermal Maximum (PETM, ~55.8±0.2 Ma) is marked by a global drop of 2-6‰ in δ13C values and rapid warming of 4-5°C in tropical surface waters and 4-8°C in high latitudes. Climate warming persisted for several tens of thousands of years and resulted in rapid diversification in terrestrial mammals and marine planktic foraminifera. Deep-water bathyal benthic foraminifera suffered a mass extinction (~40% species) but no significant extinctions occurred shallow shelf environments. Benthic extinctions are commonly explained as the effects of the initial stage of climate warming due to North Atlantic Volcanic Province volcanism (NAVP), which triggered methane release from ocean sediments causing global warming and ocean acidification. But the relationship between NAPV and the PETM events are not clearly demonstrated. Several studies [1-4] demonstrated the relationship between Hg anomalies in sediments and LIP activity associated with mass extinctions. We investigated the mercury (Hg) content of several sections located in deep bathyal (Zumaya, Trabakua, N-Spain) and outer shelf environments (Dababiya GSSP, Duwi, Egypt). At Zumaya the PETM is marked by a red clayey and marly interval poor in organic matter and coincident with a pronounced δ13C negative shift. A comparable clay interval with low TOC content is also present in the Dababyia section in the lower part of the negative δ13C shift, whereas the upper part of is enriched in TOC, reflecting increased productivity. A significant but unique Hg enrichment is observed at the onset of the PETM just below the carbone isotope shift in Spain as well as in Egypt. This increase, which is not correlated with clay or total organic carbon contents, suggests the Hg anomaly resulted from higher atmospheric Hg input into the marine realm, rather than organic matter scavenging and/or increased run-off. This Hg anomaly at the onset of the PETM provides the first direct evidence that volcanism played a crucial role in triggering the PETM events by initiating the warming that likely released methane gases that accelerated greenhouse warming and ocean acidification.

URLhttps://gsa.confex.com/gsa/2016AM/webprogram/Paper285123.html
DOI10.1130/abs/2016am-283712

Timing Tempo and Paleoenvironment Implications of Deccan Volcanism Relative to the KTB Extinction: Evidence from the Red Bole Record

TitleTiming Tempo and Paleoenvironment Implications of Deccan Volcanism Relative to the KTB Extinction: Evidence from the Red Bole Record
Publication TypeConference Paper
Year of Publication2016
AuthorsSordet, V, Adatte, T, Keller, G, Schoene, B, Samperton, KM, Khadri, S
Conference NameGeological Society of America Annual Meeting
Date Published09/2016
PublisherGeological Society of America
Other NumbersSession No. 76--Booth# 317
Abstract

Recent studies indicate that ~80% of Deccan Traps erupted over ~750 ky in magnetic polarity C29r. U-Pb zircon geochronology shows that the main phase began 250 ky before the Cretaceous-Tertiary (KT) mass extinction and continued for 500 ky into the early Danian, suggesting played a role in the mass extinction. Many lava flows are separated by red weathered horizons known as red boles that mark quiescent periods between basalt flows. Red boles have increasingly attracted the attention of researchers to understand the climatic and paleoenvironmental impact of Continental Flood Basalts. Recent advances in U-Pb dating of Deccan lava flows, studies of weathering patterns and paleoclimatic information gained from multiproxy analyses of red bole beds (e.g., lithology, mineralogy, geochemistry) yield crucial evidence of environmental changes coincident with volcanic activity.

A typical red bole begins with the fresh underlying basalt and evolves into weathered basalt, a layer of ‘bole’-shaped basalt infilled with, and overlain by, clays, which is overlain by the next lava flow. The upper clay layer is composed of red silty clays characterized by high-concentrations of immobile elements such as Al and Fe3+ that are typical of paleo-laterites, which probably developed during the short periods of weathering between eruptions. Clay minerals consist mostly of smectite suggesting semi-arid monsoonal conditions. At least 30 thick red bole layers are present between the lava flows forming the main volcanic phase. The short duration of exposure of these red boles are reflected in the mineralogical and geochemical data that indicate rapid weathering (high CIA) probably linked to increasing acid rains. ∂D and ∂18O measured on smectite clays from the red boles approximate the meteoric water composition that prevailed during Deccan eruptions. Preliminary isotopic data from these red boles suggest significant and rapid changes in rainfall intensity and/or altitude linked to the accumulation of 3400m of basalt that erupted over about 750 ky.

URLhttps://gsa.confex.com/gsa/2016AM/webprogram/Paper284642.html
DOI10.1130/abs/2016am-284642

Biostratigraphy and Impact Stratigraphy

TitleBiostratigraphy and Impact Stratigraphy
Publication TypeConference Paper
Year of Publication2016
AuthorsKeller, G
Conference NameGeological Society of America Annual Meeting
Date Published09/2016
PublisherGeological Society of America
Conference LocationDenver, Colorado
Other NumbersSession No. 43
Abstract

Today it is virtually unthinkable to solve complex geologic problems without biostratigraphy based on microfossils, whether for relative age control or environmental proxies. This is amply demonstrated for the end-Cretaceous (KTB) mass extinction where radiometric dating cannot decipher the order of events because they fall within dating error limits. But relative age dating is uniquely positioned to identify any ordered sequence of closely spaced events over a short time interval. The KTB mass extinction is one of the most easily recognized boundary events in geological history with over 300 sequences identified globally and independently verified based on the same set of five criteria originally proposed by the ICS working group during the late 1980s–1990s (mass extinction, evolution of first Danian species, d13C shift, Ir anomaly, clay layer) [1]. Despite this successful track record, placement of the KTB is contentious in areas with Chicxulub impact spherules because they are found below, at and above the KTB as a result of reworking after the primary fallout deposit [2].

As a result, biostratigraphy has come under attack by what could be called impact exuberance driven by the belief that the Chicxulub impact caused the KTB mass extinction and therefore must be KTB in age. Accordingly, some micropaleontologists proposed to redefine the KTB solely based on the ‘‘Ir anomaly associated with a major extinction horizon’’ [3], or any impact signals “in order to solve problems with correlation” [4]. But rather than solving problems this has introduced circular reasoning as the defining criteriaChicxulub caused the mass extinction, therefore Chicxulub is KTB in age. This leaves no room for determining the actual age of the Chicxulub impact. Because impact signals are subject to erosion and reworking as evident in all Chicxulub impact deposits [5,6], determining the age relative to the KTB necessarily depends on biostratigraphy to sort the relative sequence of events [7]. Impact stratigraphy cannot stand on its own without the relative dating of biostratigraphy.

URLhttps://gsa.confex.com/gsa/2016AM/webprogram/Paper283457.html
DOI10.1130/abs/2016am-283457

Discovery of a pristine Chicxulub impact glass spherule deposit on Gorgonilla Island, Colombia, in the Eastern Pacific Ocean

TitleDiscovery of a pristine Chicxulub impact glass spherule deposit on Gorgonilla Island, Colombia, in the Eastern Pacific Ocean
Publication TypeConference Proceedings
Year of Conference2015
AuthorsD., BH, Keller, G, Stinnesbeck, W, García, J, .Trieloff, M, Rodríguez, JV, Bolívar, L, Mateo, MP, Adatte, T
Conference NameGeological Society of America Annual Meeting
Volume47
Number of Volumes7
Date Published11/2015
PublisherGeological Society of America
Conference LocationBaltimore, Maryland
Other NumbersRef: Abstract No: 261829
Abstract

The discovery of a new Cretaceous/Paleogene (K/Pg) bathyal marine sequence on Gorgonilla Island, SW Colombia, extends the presence of Chicxulub spherule deposits to northern South America and to the Eastern Pacific Ocean. At the time of the Chicxulub impact, Gorgonilla was located approximately 2700-3000 km SW of the impact site.

The Gorgonilla spherule layer is approximately 2 cm thick and consists of extraordinarily well-preserved glass spherules up to 1.1 mm in diameter. The size, morphology and chemical composition of these spherules are similar to Chicxulub spherule ejecta from US, Mexico, North and Central America, and the Caribbean, but differ in their unrivaled excellent preservation. About 70-90 % of the spherules are unaltered or only partly altered consisting of colorless or faintly green to yellow glass, and their chemical composition is consistent with other occurrences, e.g. Beloc glasses. The normal size-gradation, presence of delicate spherule textures including welded components quenched from melt, and near absence of bioturbation or traction transport indicate that the basal portion of the Gorgonilla spherule layer represents a nearly unaltered primary air-fall ejecta deposit, not affected by significant reworking.

Age control based on planktic foraminifera indicate a diverse latest Maastrichtian Plummerita hantkeninoides zone CF1 assemblage below the glass spherule layer and an early Danian Parvularugoglobigerina eugubina zone P1a(2) assemblage above including Parasubbotina pseudobulloides and Subbotina triloculinoides, which evolved in the uppermost part of C29r. Maastrichtian planktic foraminifera are present in the spherule layer and clasts with earliest Danian species are present above it marking erosion. These data indicate that spherule deposition could have occurred anytime between the latest Maastrichtian zone CF1 and the early Danian P1a(2), an interval spanning about 200 ky across the K/Pg.  PDF

URLhttps://gsa.confex.com/gsa/2015AM/webprogram/Paper261829.html

Deccan Volcanism, Chicxulub Impact, Climate Change and the end-Cretaceous Mass Extinction

TitleDeccan Volcanism, Chicxulub Impact, Climate Change and the end-Cretaceous Mass Extinction
Publication TypeConference Paper
Year of Publication2015
AuthorsKeller, G, Punekar, J, Mateo, P, Adatte, T, Spangenberg, J
Conference NameEGU General Assembly Conference Abstracts
Abstract

Age control for Deccan volcanism, associated global climate changes, high-stress conditions and the KTB mass extinction is excellent based on biostratigraphy and corroborated by new U-Pb dating providing new evidence for a complex mass extinction scenario. The massive Deccan eruptions of phase-2 began in the latest Maastrichtian C29r and ended at or near the Cretaceous-Tertiary boundary (KTB) depositing ~3000 m of stacked lava flows or 80% of the total Deccan eruptions over a period of just 250 ky. The onset of phase-2 eruptions coincided with rapid global warming on land (8°C) and oceans (4°C) and increasingly high-stress environments evident by dwarfed species and decreased diversity preceding the mass extinction in planktic foraminiferal zones CF2-CF1. Deep cores in the Krishna-Godavari Basin, SE India, document the rapid mass extinction of planktic foraminifera in intertrappean sediments between four major volcanic eruptions known as the longest lava flows on Earth. Maximum stress is observed globally approaching the end of the Maastrichtian with faunal assemblages dominated (~90%) by the disaster opportunist Guembelitria cretacea. This interval correlates with the massive eruptions of the world's longest lava flows, renewed rapid global warming and ocean acidification during the last ~50 ky of the Maastrichtian. The Chicxulub impact occurred during the global warming near the base of zone CF1 preceding the mass extinction by <100 ky (depending on the time scale used). This age estimate is based on the stratigraphically oldest impact spherule layer in NE Mexico, Texas, and Yucatan crater core Yaxcopoil-1. In all other regions (e.g., North Atlantic, Caribbean, Belize, Guatemala, southern Mexico) impact spherules are reworked in early Danian sediments (zone P1a) at least 100 ky after the KTB due to Gulf Stream erosion and increased tectonic activity in the region. No species extinctions are associated with the Chicxulub impact. Any KTB mass extinction scenario must take into account both Deccan volcanism and the Chicxulub impact. The age of this impact is controversial though generally assumed to be precisely at the KTB and the sole cause of the mass extinction. This assumption is no longer valid given the short duration of massive Deccan eruptions, and the dramatic climatic and environmental effects over just 250 ky ending with the mass extinction. The pre-KTB age of the Chicxulub impact rules out a direct role in the mass extinction, although the additional CO2 and SO2 emissions likely exacerbated the ongoing Deccan climate warming. The KTB kill mechanism was likely ocean acidification resulting in the carbonate crisis commonly considered the primary cause for four of the five Phanerozoic mass extinctions.

URLhttp://adsabs.harvard.edu/abs/2015EGUGA..17.6774K

Timing, tempo and paleoenvironmental influence of Deccan volcanism relative to the KT extinction

TitleTiming, tempo and paleoenvironmental influence of Deccan volcanism relative to the KT extinction
Publication TypeConference Paper
Year of Publication2015
AuthorsAdatte, T, Keller, G, Schoene, B, Khadri, S
Conference NameEGU General Assembly Conference Abstracts
Abstract

Deccan Traps erupted in three main phases with 6% total Deccan volume in phase-1 (base C30n), 80% in phase-2 (C29r) and 14% in phase-3 (C29n). 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., 2008). Moreover, U-Pb zircon geochronology shows that the main Phase 2 began 250 ka before the Cretaceous-Tertiary (KT) mass extinction, suggesting a cause-and-effect relationship (Blair et al., 2015). In India a strong floral response is observed as a direct consequence of volcanic phase-2. In Lameta (infratrappean) sediments preceding the volcanic eruptions, palynoflora are dominated by gymnosperms and angiosperms (Samant and Mohabey, 2005). Shortly after the onset of Deccan phase-2, this floral association was decimated as indicated by a sharp decrease in pollen and spores coupled with the appearance of fungi, which mark increasing stress conditions apparently as a direct result of volcanic activity. The inter-trappean sediments corresponding to the Phases 2 and 3 are characterized by the highest alteration CIA index values suggesting increased acid rains due to SO2 emissions. Closer to the eruption center, the lava flows are generally separated by red weathered horizons known as red boles, marking a quiescent period between two basalt flows. Red boles consist mainly of red silty clays characterized by concentrations of immobile elements such as Al and Fe3+ ions, which provide indirect evidence of a primitive form of paleo-laterite that probably developed during the short periods of weathering between eruptions. There are at least 15 thick red bole layers in C29r below the KT boundary, and all were deposited in phase-2 volcanic eruptions that occurred over a time span of about 250 ky. These short duration exposures are reflected in the mineralogical and geochemical data that indicate rapid weathering (high CIA) but arid conditions. The arid conditions can be explained by acid rain, which accelerated the weathering process. 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, thus increasing biotic stress that predisposed faunas to eventual extinction at the KTB.

URLhttp://adsabs.harvard.edu/abs/2015EGUGA..17.5372A

Paleoenvironmental and paleoclimatic changes associated with the Deccan Volcanism, examples from terrestrial deposits from Central India

TitlePaleoenvironmental and paleoclimatic changes associated with the Deccan Volcanism, examples from terrestrial deposits from Central India
Publication TypeConference Paper
Year of Publication2015
AuthorsFantasia, A, Adatte, T, Spangenberg, JE, Font, E, Samant, B, Mohabey, D, Thakre, D, Keller, G
Conference NameEGU General Assembly Conference Abstracts
Abstract

Since the 80's, numerous authors have established the connection between Deccan volcanism in India and the KT events. Chenet et al (2008) showed that Deccan Traps erupted in three main phases with 6% total Deccan volume in phase-1 (base C30n), 80% in phase-2 (C29r) and 14% in phase-3 (C29n). Recent works indicate that the main phase-2 (80%) occurred over a relatively short time interval in magnetic polarity C29r, which coincides with the KTB events (Blair et al., in press, Keller et al, 2012). The biotic evolution is well understood in marine environments, but only few data are available concerning the terrestrial environmental changes. In central India, sedimentary beds associated with the Deccan Traps are represented by infratrappean (Lameta Formation) and intertrappean sediments, which were deposited during periods of volcanic quiescence. These deposits are located at different stratigraphic levels within the basaltic pile and are therefore crucial to evaluate the changes on land induced by the onset of the volcanism. The sedimentary beds exposed in the central part of India in the Jabalpur-Mandla-Chhindwara sector (Madyha Pradesh) and in the Nand-Dongargaon basin (Maharashtra) were studied using a sedimentological, geophysical, geochemical and mineralogical approach. Our results indicate that the intertrappean sediments deposited during the Deccan volcanism do not reflect the same characteristics than the infratrappean sediments preceding the volcanic eruptions. Indeed, palynological studies of the Lameta Formation indicate a dominance of angiosperms and a rich canopy of gymnosperms (Conifers and Podocarpaceae) and an understory of palms and herbs. Moreover, sedimentological and mineralogical observations indicate alluvial-limnic environment under arid climate. The eruption of Deccan volcanic flows severely affected the environmental conditions. Intertrappean sediments associated with the three Deccan phases were deposited in terrestrial to lacustrine environments under arid climate with contrasted seasons alternating dry and humid cycles, which are highlighted by the predominance of smectites, resulting from the basalt alteration. Rockeval analyses show that organic matter is well preserved in the sediments deposited between phase-1 and 2 and reflect a mixed source of lacustrine organic matter and terrestrial inputs. In contrast, the subsequent intertrappean sediments exhibit a sharp decrease in pollen and spores coupled with the appearance of fungi, which mark increasing stress conditions apparently as a direct result of volcanic activity. The organic matter analyses indicate a strong degradation suggesting that the biomass was probably oxidized by the strong volcanic activity and acidic conditions. These intertrappean sediments, corresponding to phase-2 and phase-3 (85% of Deccan basalt emissions), are characterized by the highest alteration CIA index values. Values of mass specific magnetic susceptibility are two order lower than analogue lake sediments developed under basaltic bedrock, suggesting phenomena of iron oxides dissolution by reduction/acidity. This is probably better explained by increased acid rains due to SO2 emissions than a global climatic shift; since clay minerals from the corresponding sediments do not reflect a significant climatic change. This increased alteration is coeval with the sharp decline in pollen and an increase in fungal spores and corresponds to the main phase of Deccan activity.  PDF

Fine-tuning Late Maastrichtian Faunal upheavals, climatic events and major volcanic episodes

TitleFine-tuning Late Maastrichtian Faunal upheavals, climatic events and major volcanic episodes
Publication TypeConference Proceedings
Year of Conference2015
AuthorsPunekar, J, Keller, G, Fantasia, A, Mateo, P, Spangenberg, J, Adatte, T
Conference NameGeological Society of America Annual Meeting
Volume47
Number of Volumes7
Date Published11/2015
PublisherGeological Society of America
Conference LocationBaltimore, Maryland
Other NumbersRef: Abstract No: 262776
Abstract

Highly diversified planktic foraminiferal assemblages (~65 species) prevailed in the early late Maastrichtian (mid C31n, ~68.8 Ma) at the South Atlantic DSDP Site 525A. A rapid warming (~2°C deep water) at the base CF4/ top C31n is associated with carbonate dissolution and enhanced planktic test-fragmentation indicative of ocean acidification. A subsequent cooling (~1 °C deep water) resulted in a faunal turnover and minor extinction event (base C30n, upper CF4), marked by the disappearance of Archeoglobigerina cretacea, Globotruncana bulloides, G. gandolfi nsp., Contusotruncana fornicata, C. plummerae, and C. plicata. Increased environmental stress in upper zone CF4 is supported by species dwarfing, presence of Guembelitria cretacea in open marine settings and a marked increase in the abundance of low oxygen tolerant species such as Heterohelix navarroensis (~30%) and Pseudoguembelina costulata (~15%).

The dissolution event (base CF4) and high stress environment and extinctions (top CF4) can be traced through the Tethys (Egypt, Israel) to the Indian Ocean (DSDP Site 217 and the Cauvery basin, SE India). In the Tethys (Egypt), correlative high stress conditions in shallow marine settings are recorded by G. cretacea blooms (40-60%) and a decline in the relative abundance of globotruncanids (20%). In the Indian Ocean, the onset of severe faunal stress and intense carbonate dissolution (base CF4) is associated with ongoing Ninetyeast Ridge volcanism. Environmental and faunal changes of the early Late Maastrichtian that have long remained an enigma can now be linked to at least two events – Ninetyeast Ridge volcanism and the onset of Deccan Trap volcanism. Other potentially coeval volcanic episodes yet to be investigated include Eightyeast Ridge, Southern Indian Ocean, and Andean volcanism. Absolute ages (U-Pb) of these volcanic events are vital to confirm this association.

URLhttps://gsa.confex.com/gsa/2015AM/webprogram/Paper262776.html

The last 250 kyr before the end-Cretaceous Mass Extinction

TitleThe last 250 kyr before the end-Cretaceous Mass Extinction
Publication TypeConference Proceedings
Year of Conference2015
AuthorsKeller, G, Punekar, J, Mateo, P, Adatte, T, Font, E, Spangenberg, J
Conference NameGeological Society of America Annual Meeting
Volume47
Number of Volumes7
Date Published11/2015
PublisherGeological Society of America
Conference LocationBaltimore, Maryland
Other NumbersRef: Abstract No: 262691
Abstract

The cause for the end-Cretaceous mass extinction (KTB) has long been attributed solely to the Chicxulub impact based on two major assumptions: (1) the Chicxulub impact trumped any earth-derived potential cause, and (2) Deccan volcanism played no significant role. Both of these assumptions have been challenged in recent years based on evidence that: (a) the Chicxulub impact predates the mass extinction, (b) the mass extinction occurred directly between massive Deccan eruptions and (c) U-Pb dating of Deccan lava flows revealed over 3200m of basalts accumulated during magnetochron C29r (736 ± 37 ky) with bulk eruptions over just 250 ky preceding the KTB. In 2015 these findings led the Berkeley impact group to revise the impact hypothesis by proposing that Chicxulub triggered the Deccan eruptions that led to the mass extinction, though caution that no evidence for this scenario exists to date.

Here we examine the environmental events during the 250 ky that preceded the mass extinction. Deccan volcanism occurred in three phases (C30n, C29r, C29n). We are concerned here with just the main phase-2 that erupted >1.1 million km3 basalts (80% of total by volume) depositing ~3000 m of stacked lava flows over a period of only 250 ky. Deccan phase-2 eruptions caused rapid though fluctuating global warming of 8°C on land and 4°C in the oceans sandwiched between hyperthermal warming at the base C29r and ending with a hyperthermal warming prior to the KTB.

On a global basis, planktic foraminiferal assemblages show increasingly high-stress environments in CF2-CF1 evident by dwarfed species, decreased diversity, blooms of the disaster opportunist Guembelitria cretacea, and near disappearance of large, robust species particularly in zone CF1 preceding the mass extinction. During the last 30-50 ky before the mass extinction, hyperthermal warming, decreased species diversity and abundance, shell dissolution and ocean acidification, low magnetic susceptibility and high mercury concentrations have all been linked to the most intense phase of Deccan volcanism. These data demonstrate that the KTB mass extinction was not an instantaneous event but occurred over a few thousand to several tens of thousands of years ending at the KTB. The Chicxulub impact can no longer be considered the sole cause, or even primary cause for this mass extinction event

URLhttps://gsa.confex.com/gsa/2015AM/webprogram/Paper262691.html

Paleoenvironmental influence of Deccan volcanism relative to the KT extinction

TitlePaleoenvironmental influence of Deccan volcanism relative to the KT extinction
Publication TypeConference Proceedings
Year of Conference2015
AuthorsAdatte, T, Keller, G, Schoene, B, Samperton, K, Font, E, Sial, AN, De Lacerada, LD, Punekar, J, Fantasia, A, Khadri, S
Conference NameGeological Society of America Annual Meeting
Volume47
Number of Volumes7
Date Published11/2015
PublisherGeological Society of America
Conference LocationBaltimore, Maryland
Other NumbersRef: Abstract No: 265331
Abstract

Deccan Traps erupted in three main phases with 6% total Deccan volume in phase-1 (C30n), 80% in phase-2 (C29r) and 14% in phase-3 (C29n). Recent studies indicate that the bulk (80%) of Deccan trap eruptions (Phase-2) occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology shows that the main Phase 2 began 250 ky before the Cretaceous-Tertiary (KT) mass extinction, suggesting a cause-and-effect relationship.

In India a strong floral response is observed as a direct consequence of volcanic phase-2. Shortly after the onset of Deccan Phase 2, the floral association dominated by gymnosperms and angiosperms was decimated as indicated by a sharp decrease in pollen and spores coupled with the appearance of fungi, which mark increasing stress conditions as a direct result of volcanic activity. The inter-trappean sediments deposited in Phase 2 are characterized by the highest alteration CIA index values suggesting increased acid rains due to SO2 emissions. Closer to the eruption center, the lava flows are generally separated by red weathered horizons known as red boles, marking quiescent periods between basalt flows.

Red boles consist mainly of red silty clays characterized by concentrations of immobile elements such as Al and Fe3+ ions, typical of paleo-laterite that probably developed during the short periods of weathering between eruptions. At least 15 thick red bole layers are present in C29r below the KT boundary. All of these were deposited during phase-2 volcanic eruptions that occurred over a time span of about 250 ky. The short duration exposures of these red boles are reflected in the mineralogical and geochemical data that indicate rapid weathering (high CIA) linked to increasing acid rains.

Global geochemical effects of Deccan volcanism have been detected in the marine sedimentary record. At Bidart (France), high mercury (Hg) of volcanic origin characterizes the sedimentary interval located below the Iridium-rich layer where low magnetic susceptibility was hypothesized to result from paleoenvironmental perturbations linked to paroxysmal Deccan phase-2. These elevated Hg concentrations correlate with high shell fragmentation and dissolution effects in planktic and benthic foraminifera indicating that ocean acidification drastically affected marine biodiversity.

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