end-Triassic Mass Extinction Event Research Articles

Synchronous Wildfire Activity Rise and Mire Deforestation at the Triassic–Jurassic Boundary

The end-Triassic mass extinction event (∼201.4 million years ago) caused major faunal and floral turnovers in both the marine and terrestrial realms. The biotic changes have been attributed to extreme greenhouse warming across the Triassic–Jurassic (T–J) boundary caused by massive release of carbon dioxide and/or methane related to extensive volcanism in the Central Atlantic Magmatic Province (CAMP), resulting in a more humid climate with increased storminess and lightning activity. Lightning strikes are considered the primary source of wildfires, producing charcoal, microscopically recognized as inertinite macerals. The presence of polycyclic aromatic hydrocarbons (PAHs) of pyrolytic origin and allochthonous charcoal in siliciclastic T–J boundary strata has suggested widespread wildfire activity at the time. We have investigated largely autochthonous coal and coaly beds across the T–J boundary in Sweden and Denmark. These beds consist of predominantly organic material from the in situ vegetation in the mires, and as the coaly beds represent a substantial period of time they are excellent environmental archives. We document a remarkable increase in inertinite content in the coal and coaly beds across the T–J boundary. We show estimated burning temperatures derived from inertinite reflectance measurements coupled with palynological data and conclude that pre-boundary late Rhaetian mire wildfires included high-temperature crown fires, whereas latest Rhaetian–Sinemurian mire wildfires were more frequent but dominated by lower temperature surface fires. Our results suggest a major change in the mire ecosystems across the T–J boundary from forested, conifer dominated mires to mires with a predominantly herbaceous and shrubby vegetation. Contrary to the overall regional vegetation for which onset of recovery commenced in the early Hettangian, the sensitive mire ecosystem remained affected during the Hettangian and did not start to recover until around the Hettangian–Sinemurian boundary. Decreasing inertinite content through the Lower Jurassic suggests that fire activity gradually resumed to considerable lower levels.

No causal link between terrestrial ecosystem change and methane release during the end-Triassic mass extinction

Research Article| June 01, 2012 No causal link between terrestrial ecosystem change and methane release during the end-Triassic mass extinction Sofie Lindström; Sofie Lindström * 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark *E-mail: sli@geus.dk. Search for other works by this author on: GSW Google Scholar Bas van de Schootbrugge; Bas van de Schootbrugge 2Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, D-60438 Frankfurt, Germany Search for other works by this author on: GSW Google Scholar Karen Dybkjær; Karen Dybkjær 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Search for other works by this author on: GSW Google Scholar Gunver Krarup Pedersen; Gunver Krarup Pedersen 3Department of Geography and Geology, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Search for other works by this author on: GSW Google Scholar Jens Fiebig; Jens Fiebig 2Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, D-60438 Frankfurt, Germany Search for other works by this author on: GSW Google Scholar Lars Henrik Nielsen; Lars Henrik Nielsen 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Search for other works by this author on: GSW Google Scholar Sylvain Richoz Sylvain Richoz 4CPSOE, Austrian Academy of Science, c/o University of Graz, Heinrichstrasse 26, 8020 Graz, Austria Search for other works by this author on: GSW Google Scholar Author and Article Information Sofie Lindström * 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Bas van de Schootbrugge 2Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, D-60438 Frankfurt, Germany Karen Dybkjær 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Gunver Krarup Pedersen 3Department of Geography and Geology, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Jens Fiebig 2Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, D-60438 Frankfurt, Germany Lars Henrik Nielsen 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Sylvain Richoz 4CPSOE, Austrian Academy of Science, c/o University of Graz, Heinrichstrasse 26, 8020 Graz, Austria *E-mail: sli@geus.dk. Publisher: Geological Society of America Received: 17 Oct 2011 Revision Received: 29 Dec 2011 Accepted: 11 Jan 2012 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2012 Geological Society of America Geology (2012) 40 (6): 531–534. https://doi.org/10.1130/G32928.1 Article history Received: 17 Oct 2011 Revision Received: 29 Dec 2011 Accepted: 11 Jan 2012 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Sofie Lindström, Bas van de Schootbrugge, Karen Dybkjær, Gunver Krarup Pedersen, Jens Fiebig, Lars Henrik Nielsen, Sylvain Richoz; No causal link between terrestrial ecosystem change and methane release during the end-Triassic mass extinction. Geology 2012;; 40 (6): 531–534. doi: https://doi.org/10.1130/G32928.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Profound changes in both marine and terrestrial biota during the end-Triassic mass extinction event and associated successive carbon cycle perturbations across the Triassic-Jurassic boundary (T-J, 201.3 Ma) have primarily been attributed to volcanic emissions from the Central Atlantic Magmatic Province and/or injection of methane. Here we present a new extended organic carbon isotope record from a cored T-J boundary succession in the Danish Basin, dated by high-resolution palynostratigraphy and supplemented by a marine faunal record. Correlated with reference C-isotope and biotic records from the UK, it provides new evidence that the major biotic changes, both on land and in the oceans, commenced prior to the most prominent negative C-isotope excursion. If massive methane release was involved, it did not trigger the end-Triassic mass extinction. Instead, this negative C-isotope excursion is contemporaneous with the onset of floral recovery on land, whereas marine ecosystems remained perturbed. The decoupling between ecosystem recovery on land and in the sea is more likely explained by long-term flood basalt volcanism releasing both SO2 and CO2 with short- and long-term effects, respectively. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The end Triassic mass extinction record of Williston Lake, British Columbia

Triassic–Jurassic boundary sections on the shore of Lake Williston, British Columbia record a spectrum of depositional environments from the western Canadian continental margin. A primarily deep-water, anoxic record of deposition, indicated by V/V + Ni, V/Cr, Th/U indices and pyrite framboid and facies data, is seen throughout the Late Triassic–Early Jurassic (Norian-Hettangian) interval in a section at Black Bear Ridge. Abundant Monotis bivalve populations in Norian strata are interpreted to have lived on the seabed during transient oxygenation events that punctuated the background anoxic conditions. Monotis went extinct around the Norian/Rhaetian boundary and the deep-water assemblages are subsequently dominated by thin-shelled pectinids. An intra-Rhaetian sea-level fall generated a major hiatus in the proximal Black Bear Ridge section whilst distinctive lowstand strata were developed in the more distal and more complete Ne Parle Pas Point and Pardonet Creek sections. These consist of shallow-water, phosphatic ooid sand facies that contain diverse bivalves. The majority of the infaunal bivalves (but not the epifaunal ones) disappeared at the acme of the regression. This is the end-Triassic mass extinction event and it occurred shortly before a terminal Triassic flooding event. This transgressive event is associated with a rapid negative shift of δ 13C org values interpreted to be the Initial Isotope Excursion of Hesselbo et al. [Hesselbo, S.P., Robinson, S.A., Surlyk, F., Piasecki, S., 2002. Terrestrial and marine extinction at the Triassic-Jurassic boundary synchronized with major carbon-cycle perturbation: a link to initiation of massive volcanism? Geology 30, 251–254]. The Rhaetian record of Williston Lake thus records an extinction of shallow-water infaunal bivalves during a lowstand prior to the development of a transgressive record that is associated with a major, negative C isotope.

Progress and review of the studies on the end-Triassic mass extinction event

The mass extinction at the end-Triassic is one of the five biggest in the Phanerozoic However it is the least well understood among these five events, and only till last decade it became a great academic interesting subject to geologists. The evidences for this event come obviously from bivalves, brachiopods, ammonites, corals, radiolaria, ostracods and foraminifera of marine habitats, and plants and tetrapods of terrestrial realm. By contrast, for some of other groups, such as marine gastropods and marine vertebrates, no mass extinction has been recognized yet. The extinction event is strongly marked at specific level but shown a complicated situation at generic and family levels. Dramatic changing of the environment, such as the temperature raise due to the greenhouse effect, the marine anoxic habitats caused by a sudden transgression after the regression at the end of Triassic, has been claimed to be the main cause of the extinction. Many hypotheses have been suggested to demonstrate the mechanisms of the environment changing, among which two popular ones are the bolide impact and volcanic eruption.

Assessing the record and causes of Late Triassic extinctions

Accelerated biotic turnover during the Late Triassic has led to the perception of an end-Triassic mass extinction event, now regarded as one of the “big five” extinctions. Close examination of the fossil record reveals that many groups thought to be affected severely by this event, such as ammonoids, bivalves and conodonts, instead were in decline throughout the Late Triassic, and that other groups were relatively unaffected or subject to only regional effects. Explanations for the biotic turnover have included both gradualistic and catastrophic mechanisms. Regression during the Rhaetian, with consequent habitat loss, is compatible with the disappearance of some marine faunal groups, but may be regional, not global in scale, and cannot explain apparent synchronous decline in the terrestrial realm. Gradual, widespread aridification of the Pangaean supercontinent could explain a decline in terrestrial diversity during the Late Triassic. Although evidence for an impact precisely at the boundary is lacking, the presence of impact structures with Late Triassic ages suggests the possibility of bolide impact-induced environmental degradation prior to the end-Triassic. Widespread eruptions of flood basalts of the Central Atlantic Magmatic Province (CAMP) were synchronous with or slightly postdate the system boundary; emissions of CO 2 and SO 2 during these eruptions were substantial, but the contradictory evidence for the environmental effects of outgassing of these lavas remains to be resolved. A substantial excursion in the marine carbon-isotope record of both carbonate and organic matter suggests a significant disturbance of the global carbon cycle at the system boundary. Release of methane hydrates from seafloor sediments is a possible cause for this isotope excursion, although the triggering mechanism and climatic effects of such a release remain uncertain.

Radiations and extinctions in relation to environmental change in the marine Lower Jurassic of northwest Europe

A diversity and turnover analysis has been undertaken for a number of invertebrate groups in the Liassic of northwest Europe. There is a more or less steady rise in diversity from the early Hettangian through to the Pliensbachian, followed by a marked decline into the early Toarcian, after which it tends once more to increase. Ammonites stand out from the other invertebrates as having had an exceptionally high rate of turnover, with very short species durations.Increase of neritic habitat area due to rise of sea level, and recolonization following the end-Triassic mass extinction event appear to be the promoters of diversity increase or radiation. Severe reductions of neritic habitat area with associated environmental deterioration, related either to episodic marine regressions or spreads of anoxic bottom waters, and bound up respectively with sea-level fall and rise, are seen as the prime factors responsible for increase of extinction rate. While the environmentally sensitive ammonites were affected by even minor regressions, the other, more eurytopic groups were evidently more resistant to these. The only event that warrants the term mass extinction, affecting nearly all the benthos and nekton but not the plankton, correlates precisely with the early Toarcian anoxic event. Several episodes can be recognized of migrations of organisms into Europe following extinctions.