On the end-Triassic mass extinction – In Danish

This spring an entire issue of the Danish Geoscience journal Geoviden was dedicated to our research project “The Triassic–Jurassic boundary: Impact of a Large Igneous Province on the geobiosphere”. Geoviden is a popular science magazine aimed at high school students and everyone else interested in geology and geography. Our issue is called “A crisis in the history of life” and  presents the background, hypothesis and progress of our Geocenter Denmark financed project. Unfortunately for non-Scandinavian readers it is in Danish. It is richly illustrated and covers various aspects of our research. It can be downloaded for free using this link, so feel free to check it out: Geoviden No 1 2016: “En krise i livets historie”

GEOVIDEN_1_2016

Front page illustration by Stefan Sølberg, GEUS.

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Drilling through Triassic-Jurassic boundary strata

On Tuesday next week we launch our new core drilling project. This time we are going to drill through the lowermost Jurassic sedimentary succession at Sose Bugt on the Danish island of Bornholm, with the aim to reach uppermost Triassic rocks. Despite many excellent geological studies in the area it is not clear if the Triassic-Jurassic boundary is preserved on the Sose Fault block, but the presence of Hettangian-Sinemurian strata in the coastal cliffs at Sose Bugt and Upper Triassic green and red clays along parts of the coast make it an ideal area to drill for the TJB.

Our core drilling project is funded by Geocenter Denmark and is a part of our research project on the end-Triassic mass extinction event. The core drilling will provide us with new research material, hopefully both of the mass extinction interval and of the recovery in the earliest Jurassic.

Quite excited about this! 🙂

Beautiful Hettangian (lowermost Jurassic) clays and sands at Sose Bugt, Bornholm, Denmark (Photo: Sofie Lindström)

Beautiful Hettangian (lowermost Jurassic) clays and sands at Sose Bugt, Bornholm, Denmark (Photo: Sofie Lindström)

EGU2014 Thursday: “Volcanism, Impacts, Mass extinctions and Global environmental change” – a brief review of two talks.

Thursday afternoon at the EGU2014 was totally dedicated to the session “Volcanism, Impacts, Mass extinctions and Global environmental change” in which I also presented a talk. The session contained a total of eleven oral presentations covering various subject within the above mentioned topics. The first four talks were on the volcanism of the Siberian Traps and the end-Permian mass extinction event.

In the first talk, Seth Burgess presented new high-resolution geochronological data for the intrusives of the Siberian Traps. Burgess and his colleagues had used the same analysis and standards on not only zircons from the Siberian Traps, but also on zircons from the ash-layers bracketing the end-Permian mass extinction level at the GSSP Meishan in China. According to these new datings all the dated intrusives post-date the end-Triassic mass extinction event. Seth Burgess stated that although these data could be taken as “the nail in the coffin for the theory that the intrusive activity caused the mass extinction” he didn’t believe that they did. He then went on to explain that the majority of the intrusives of the Siberian Traps are situated at depths and those that have been dated are the ones that are accessible, probably producing a biased record.

This was good news for the second speaker, Henrik Svensen, who presented a talk on the sill-induced evaporite and coal metamorphism of the Siberian Traps. Svensen and colleagues showed that the Siberian Traps contain very thick sills that have been emplaced into both coal-bearing sediments and salt deposits, with the potential for degassing of both green house gases (CH4, CO2), aerosols (SO2), and ozone destructive gases (CH3Cl, CH3Br), which could explain the end-Permian biotic crisis.

A fuzzy picture of Henrik Svensen and his audience.

A fuzzy picture of Henrik Svensen and his audience.

 

Report from the GSA-meeting in Denver, and the session on the TJ-boundary and end-Triassic mass extinction

Last week I attended the Geological Society of America (GSA) annual meeting and 125th anniversary which was held at the Colorado Convention Center in Denver, Colorado, USA – A multitude of scientific sessions and thousands of geoscientists! As always with large conferences, it is both fantastic and confusing to have so many interesting sessions presented almost simultaneously.

The Colorado Convention Center in Denver with its Blue Bear and the Rockies in the background (view from my hotel window at the Regency Hyatt; Photo: S. Lindström).

The Colorado Convention Center in Denver with its Blue Bear and the Rockies in the background (view from my hotel window at the Regency Hyatt; Photo: S. Lindström).

I participated in the session T238. New insights into Triassic-Jurassic Transition events and end-Triassic Mass Extinction (blue text are links to program and abstracts). This session was graciously hosted by Rowan C. Martindale and Morgan F. Schaller who had put together an interesting programme bringing forth some of the latest research and ideas concerning TJ-boundary research. We who participated got to hear interesting talks on the carbon cycle, specifically on Late Triassic pCO2 variations by Morgan Schaller et al. and on Late Triassic ocean stability and orbital control by Sylvain Richoz et al.  The pedogenic carbonate results of Schaller et al.’s research suggest a long-time (30-million-years) fall in the atmospheric CO2-content from the Carnian to the late Rhaetian prior to the eruption of the Central Atlantic Magmatic Province (CAMP). Richoz et al., on the otherhand, demonstrate a relatively stable marine C-isotope curve from the Norian to the Rhaetian, displaying only a gentle decrease, i.e. possibly an on-going input of light carbon to the atmosphere (increased CO2) during the Late Triassic prior to CAMP eruption. 

Regarding the plant record, Wolfram Kürschner presented some new data indicating environmental mutagenesis in Late Triassic conifers in more equatorial areas, where a sudden size increase in Classopollis pollen may be due to whole genome doubling (polyploidy) as a consequence of environmental stress.  Karen Bacon talked about the fact that many present-day plants get thicker leaves when subjected to increased levels of CO2, and especially if exposed to low O2 at the same time, and put this in relation to findings in the plant records across the TJ-boundary in East Greenland. In one of the solicited talks, Jennifer McElwain presented an extensive review of her and her co-workers palaeobotanical research on the TJ-boundary of East Greenland over the last 25 years. The impact of her research did however, receive some criticism from the next solicited speaker Spencer Lucas who meant that not only is there no palaeobotanical evidence for a global or even regional mass extinction at the end of the Triassic, but not for the terrestrial terapods either! But then Lucas did not seem to acknowledge the palynological support for a floral mass extinction. His critique does emphasize that there is a need of more thorough palaeobotanical work across the TJ-boundary from other parts of the world.

Lucas also presented major criticism on the impact of the cyclostratigraphic scheme for the Newark Basin, which he said had caused “a decade-long miscorrelation” with other TJ-boundary succession. This led to a slightly heated discussion between Lucas and the next speaker, Paul Olsen, one of the researchers behind the Newark Basin cyclostratigraphy. In his talk, Paul Olsen discussed the impact a volcanic winter due to SO2-degassing from the CAMP would have on terrestrial vertebrates. 

After a short break it was finally my turn. My talk, entitled “Supraregional seismites in Triassic – Jurassic boundary strata“, presented widespread evidence of episodic seismic activity in NW Europe during the end-Triassic mass extinction interval. My co-authors and I have found evidence of at least four separate seismic events in the form of soft-sediment deformations within TJ-boundary successions from Sweden, Denmark and Germany, and the implications of these on the CAMP and the end-Triassic mass extinction where discussed during the talk, which was going as scheduled when it was interrupted by a ca 5 minute long false fire alarm. Eventually I could continue and finish my talk but unfortunately with no time for questions.

One of the most interesting talks was that on the Cotham Marble where Yadira Ibarra et al. showed that the calcified microbial mats, containing prasinophycean algal cysts (Tasmanites) and a sparse shelly fauna, must have formed in a calcium carbonate supersaturated environment. The Cotham Marble is synchronous to the so called initial C-isotope excursion. Kathleen Rittersbuch et al. presented new data on earliest Jurassic siliceous sponge dominance based on fieldwork in the Peruvian Andes. Correlations with siliceous sponge records in Nevada, the Austrian Alps and Morocco indicate that this was a globally relevant phenomena.

Aviv Bachan and Jonathan Payne presented modeling of hypothesized carbon cycle perturbation scenarios for the TJ-boundary, focusing on the large positive C-isotope excursion (CIE) following the sharp negative CIE. They found that the modelled scenario most similar to the recorded C-isotope record is that with temporary increase in pCO2 coincident with the volatile release, as well as a temporary decrease in carbonate saturation, indicating that the release of volatiles during the emplacement of the Central Atlantic Magmatic Province could have been the driver of the environmental perturbation.

The final talk of the session was that of Bas van de Schootbrugge et al. who presented our palynological reworking data that indicate increased weathering and erosion, i.e. mass-wasting, synchronous to the terrestrial deforestation during the end-Triassic mass extinction. The massive reworking registered in both Germany, Denmark and Sweden, emphasizes the severity of the environmental impact on the land environment, and it seems likely that increased input of sediment, soil and organic matter to the ocean must have played a part in the extinction scenario.

We celebrated the end of an interesting the session by having lunch at the Rock-Bottom Restaurant in downtown Denver. Good food and great company! 🙂

Global warming, ocean acidification and mass extinctions

On-going anthropogenic carbon emissions has reached levels 40% higher than pre-industrial ones in 1750, due to human burning of fossil fuels. Despite international discussions and various national efforts to decrease carbon emissions, the amount of heat-trapping carbon dioxide in the atmosphere reached a record 390.9 parts per million (ppm) in 2011, according to a report recently released by the UN’s World Meteorological Organization (WMO). As a result, 30% more  atmospheric heat was kept from escaping to space than in 1990. The increased amounts of CO2 in the atmosphere has lead to a 1°C increase in average temperatures worldwide. This may not sound much, but with the long retention time of CO2 in the atmosphere the average temperature will continue to rise for a long time even if we should manage to limit our carbon emissions extensively. The World bank estimates an average temperature rise to as much as 4°C by 2060 unless we start reducing our carbon emissions significantly! The effects of such a dramatic global warming would mean serious threats to the human civilization, with extreme weather, heat waves and sea-level rise, but that is not all…

The geological record testifies to the effects of global warming. Numerous scientific articles dealing with the causes and consequences of the mass extinctions at the end-Permian (252 million years ago) and end-Triassic (201 million years ago) have provided evidence of the dire effects of intense global warming. Both events are linked to massive volcanism from large igneous provinces (LIPs) that emitted huge amounts of CO2 and methane to the Earth’s atmosphere. As discussed by Payne and Clapham (Annual Review of Earth and Planetary Sciences, May 2012) such mass extinction events in the geological record may serve as an important ancient analog for the twenty-first century! Climate change and increased temperatures, possibly coupled with destruction of the ozone layer, can account for the extinctions on land, whereas changes in ocean oxygen levels, CO2, ocean acidification, and temperature made life difficult for marine animals, resulting in the demise of as much as 96% and 80% of all species for the end-Permian and end-Triassic events, respectively.

Recent scientific reports provide warning signals. One of the most well documented consequences of the increased CO2-levels at the end-Permian and end-Triassic events is referred to as the biocalcification crisis. The increased CO2-levels caused upper ocean acidification due to lowering of the pH of surface waters, causing problems for calcareous organisms such as calcareous phytoplankton and reef-building organisms, e.g. bivalves and corals. Scientists have long discussed the on-going coral bleeching as one result of our anthropogenic carbon emissions, but now Bednarsek et al. (Nature Geoscience, advanced on-line publication 2012) report alarming evidence of dissolution of shells on living pteropods (shell-bearing free-swimming sea-snails) in the Southern Ocean, providing further warning signals of on-going ocean acidification.

In addition, Arneborg et al. (Nature Geoscience, advanced on-line publication 2012) show increased inflow of warm and salty bottom waters to the central Amundsen shelf in Antarctica where the thinning of glaciers have persisted over the last decades. The Amundsen shelf is part of the West Antarctic Ice Sheet that contains enough ice to raise global sea level by several metres and, because it is grounded mainly below sea level, it is extra sensitive to ocean warming.

These reports, among many others, should serve as serious warning signals to world leaders that we need to take immediate action to reduce carbon emissions. So far, we have not managed to act efficiently on reducing emissions. At the UN-sponsored climate meeting in Copenhagen in 2009 the relatively weak agreement was to a non-binding target of limiting the world’s greenhouse-gas-triggered temperature increase to no more than 2°C (3.6°F) above preindustrial levels to limit the potential damage. The 2011 numbers provided by  the UN’s World Meteorological Organization (WMO) clearly show that we are failing to keep even that!

Everybody’s talking about methane…

It actually started 16 years ago when Gerald R. Dickens and his colleagues published their paper on oceanic methane hydrate dissociation and the Palaeocene-Eocene Thermal Maximum (PETM). Their hypothesis that release of methane gas stored in oceanic sediments was the cause of the negative carbon-isotope excursion at the end of the Palaeocene and hence the trigger of the global warming recorded at the PETM, got scientists working on climate change and mass extinction around the world to suddenly set their old theories aside and focus on this new one.

Burning natural gas which consists of methane to 80% (Left) and a methane molecule (right).

Today, it seems, everybody’s talking about methane, CH4, this very potent greenhouse gas. From methane stored in clathrates underneath the ocean floor, or frozen by permafrost in the circum- Arctic or Antarctic tundra ( e.g. De Conti et al. 2012), to cattle or even farting dinosaurs during the Mesozoic, it poses a severe threat to life on Earth if released in large quantities. Hence, many scientific papers (see e.g. Payne et al. 2004 and references therein, and Ruhl et al. 2011) have argued that methane must have played a role in the end-Permian and end-Triassic mass extinctions, which are both associated with negative carbon-isotope excursions indicating input of light carbon (carbondioxide or methane from volcanoes or other sources).

My colleagues and I have studied the Triassic-Jurassic (T/J) boundary of the Denmark and compared that to a well known T/J boundary succession in England. In these two areas the carbon-isotope records exhibit three negative excursions separated by two intervals with more positive carbon-isotope values. What we have found is that the most profound floral changes on land and amongst organisms in the epicontinental sea that once covered these two areas, commenced within the first positive interval, i.e. between the first negative carbon-isotope peak and the second (most prominent) one. At the same level as the second negative carbon-isotope peak, which has been attributed to methane injection by e.g. Ruhl et al. 2011, the flora does not seem to be affected but is instead recovering, while organisms in the ocean continue to suffer. Hence our study suggests a more complex scenario…

You can read our paper (or just the abstract) or the press release.

An issue of plants…

In a new issue of Nature Geoscience: Earth shaped by plants several interesting papers on plant related topics have been gathered for all us botany/palaeobotany interested geeks to feast on 🙂

The issue includes:

A feature/focus article by Timothy M. Lenton et al. on how the expansion of terrestrial vegetation in the Late Ordovician ca 440 million years ago cooled the atmosphere and triggered the growth of ice sheets.

A review article by Gibling & Davies on how the development of terrestrial vegetation changed the fluvial style of rivers and shaped the landscapes over a 250 million year period, from the Cambrian to the carboniferous.

As well as a selection of papers from the archives, amongst which are two articles dealing with the Triassic/Jurassic boundary, namely the paper by Belcher et al. (2010) on charcoal and wildfires in the T/J boundary record of Greenland, and a News and views story by Bas van de Schootbrugge (2010) discussing that very subject.

"What would life be without plants?"