Iridium Across the Triassic-Jurassic Boundary in Austria

Distribution of iridium and associated geochemistry across the Triassic–Jurassic boundary in sections at Kuhjoch and Kendlbach, Northern Calcareous Alps, Austria

Authors:

Tanner et al

Abstract:

Samples from strata spanning the Triassic–Jurassic boundary at the GSSP at Kuhjoch and at Kendlbachgraben were studied by NAA, XRF and combustion analysis to determine Ir levels and associated geochemistry. The results are compared to previously determined carbon isotope stratigraphy at these sections. Ir concentrations in the limestones of the Kössen Formation at Kuhjoch are very low (< 10 pg/g) below the top of the formation, rising to 26 pg/g, in the T-bed at the top of the Eiberg Member. The Tiefengraben Member of the Kendlbach Formation exhibits higher concentrations of Ir in general relative to the strata below. The shift to higher levels is abrupt at the base of the member, coinciding with a decrease in carbonate content. Concentrations of 60 to 80 pg/g are typical through the entire thickness of the Schattwald Beds and into the gray Tiefengraben Member strata, peaking at 145 pg/g. Concentrations decline to 30–40 pg/g above 680 cm from the formation base, coinciding with increasing carbonate content. The analyses from the Kendlbachgraben section compare well with those from Kuhjoch, with similar difference in Ir concentration between the Kössen and Kendlbach formations. In both sections, the initial increase in Ir corresponds to the initial carbon isotope excursion. Concentrations of redox-sensitive elements indicate transient reducing conditions during deposition of the uppermost Kössen Formation, but oxidizing conditions during Tiefengraben Member deposition. The Al/Ti ratio indicates more intense weathering during deposition of the lowermost 20 cm of the Tiefengraben Member, but otherwise consistently humid to sub-humid climate prevailed during deposition. The primary control on Ir concentration in the sampled section is formation lithology, although there are variations within the Tiefengraben Member that are independent of carbonate content. Enrichment of Ir at the top of the T-bed is associated with a redox boundary, but the cause of other variations is undetermined.

Central Atlantic Magmatic Province was GeoChronologically Aligned WIth Triassic Jurassic Mass Extinction

Geochemical consequences of intense pulse-like degassing during the onset of the Central Atlantic Magmatic Province

Authors:

Paris et al

Abstract:

The Triassic–Jurassic boundary (TJB) is marked by one of the five largest mass extinctions of the Phanerozoic and the eruption of a large igneous province: the Central Atlantic Magmatic Province (CAMP). The TJB is characterized by a carbonate production crisis, by negative excursions in the carbon isotopic ratio of buried organic matter, and by successive peaks in atmospheric CO2. Here we use the numerical model GEOCLIM to explore the possible connections between the CAMP emplacement and the observed carbon cycle perturbations. Different degassing scenarios linked to the CAMP eruption are explored. We show that the emission of realistic amounts of CO2 that follow a geologically constrained degassing scenario as short-term peaks (less than 10 ka) leads to successive decrease in carbonate production, as observed in the geological record. We also calculate the evolution of carbon isotopes and show that our model reproduces the amplitude of the isotopic excursion with a volcanic degassing of CO2 characterized by a carbon isotopic composition of − 20‰. Such low values could be associated to carbon pools of light isotopic composition located at the transition zone [Cartigny, P. 2010, Earth and Planetary Science Letters, v. 296, p. 329–339] and not necessarily to biogenic methane release. Finally, the model predicts a succession of short-term CO2 rises, with an amplitude in close agreement with available proxy-based reconstructions.

Evidence of Orbital Climate Forcing at the Triassic/Jurassic Boundary

Triassic–Jurassic climate in continental high-latitude Asia was dominated by obliquity-paced variations (Junggar Basin, Ürümqi, China)

Authors:

Sha et al

Abstract:

Empirical constraints on orbital gravitational solutions for the Solar System can be derived from the Earth’s geological record of past climates. Lithologically based paleoclimate data from the thick, coal-bearing, fluvial-lacustrine sequences of the Junggar Basin of Northwestern China (paleolatitude ∼60°) show that climate variability of the warm and glacier-free high latitudes of the latest Triassic–Early Jurassic (∼198–202 Ma) Pangea was strongly paced by obliquity-dominated (∼40 ky) orbital cyclicity, based on an age model using the 405-ky cycle of eccentricity. In contrast, coeval low-latitude continental climate was much more strongly paced by climatic precession, with virtually no hint of obliquity. Although this previously unknown obliquity dominance at high latitude is not necessarily unexpected in a high CO2 world, these data deviate substantially from published orbital solutions in period and amplitude for eccentricity cycles greater than 405 ky, consistent with chaotic diffusion of the Solar System. In contrast, there are indications that the Earth–Mars orbital resonance was in today’s 2-to-1 ratio of eccentricity to inclination. These empirical data underscore the need for temporally comprehensive, highly reliable data, as well as new gravitational solutions fitting those data.

Awesome Triassic-Jurassic Mass Extinction Picture

Credit Victor Leshyk.

 The related paper.

Massive Earthquake(s?) at the Triassic-Jurassic Extinction

Intense and widespread seismicity during the end-Triassic mass extinction due to emplacement of a large igneous province

Authors:

Lindström et al

Abstract:

Multiple levels of earthquake-induced soft-sediment deformations (seismites) are concentrated in the end-Triassic mass extinction interval across Europe. The repetitive nature of the seismites rules out an origin by an extraterrestrial impact. Instead, this intense seismic activity is linked to the formation of the Central Atlantic magmatic province (CAMP). By the earliest Jurassic the seismic activity had ceased, while extrusive volcanism still continued and biotic recovery was on its way. This suggests that magmatic intrusions into sedimentary strata during early stages of CAMP formation caused emission of gases (SO2, halocarbons, polycyclic aromatic hydrocarbons) that may have played a major part in the biotic crisis.

Episodic Photic Zone Marine Euxinia During the Triassic-Jurassic Mass Extinction

Episodic photic zone euxinia in the northeastern Panthalassic Ocean during the end-Triassic extinction

Authors:

Kasprak et al

Abstract:

Severe changes in ocean redox, nutrient cycling, and marine productivity accompanied most Phanerozoic mass extinctions. However, evidence for marine photic zone euxinia (PZE) as a globally important extinction mechanism for the end-Triassic extinction (ETE) is currently lacking. Fossil molecular (biomarker) and nitrogen isotopic records from a sedimentary sequence in western Canada provide the first conclusive evidence of PZE and disrupted biogeochemistry in neritic waters of the Panthalassic Ocean during the end Triassic. Increasing water-column stratification and deoxygenation across the ETE led to PZE in the Early Jurassic, paralleled by a perturbed nitrogen cycle and ecological turnovers among noncalcifying groups, including eukaryotic algae and prokaryotic plankton. If such conditions developed widely in the Panthalassic Ocean, PZE might have been a potent mechanism for the ETE.

More Information About the Hettangian Jurassic/Post Triassic-Jurassic Mass Extinction Sponge Bob World

Andean sponges reveal long-term benthic ecosystem shifts following the end-Triassic mass extinction

Authors:

Ritterbush et al

Abstract:

Thick cherts and cherty dolomites in the basal Jurassic Aramachay Formation of Peru preserve a thriving continental shelf community dominated by siliceous sponges that followed the end-Triassic collapse of metazoan-rich carbonate accumulation. Similar Hettangian and Sineumurian deposits from Nevada, U.S.A., Austria, and Morocco suggest that an Early Jurassic siliceous sponge takeover was a widespread phenomenon that persisted for ~ 2 m.y. until metazoan-driven carbonate sedimentation recovered. The post-extinction dominance of siliceous sponges likely resulted from the confluence of metazoan carbonate reef collapse (removal of incumbents) and geochemical conditions that fostered the success of the siliceous sponge-dominated ecosystem. Simple mass balance calculations suggest the siliceous sponge takeover was likely permitted by an increased silica flux as a consequence of weathering Central Atlantic Magmatic Province (CAMP) basalts. The CAMP basalts alone could supply all the silica needed to sustain the sponge takeover, although contributions were also likely from increased hot-climate weathering of other silicates and possible reductions in dissolved silica demand by radiolarians. Detailed sedimentological, fossil, and microfacies analyses were conducted at six field sites across a shallow shelf system recorded in the central Peruvian Andes (Yauli Dome), focusing on the metazoan contribution to sedimentation. Sedimentary structures at all six sites demonstrated on-shelf deposition, similar to the underlying upper Triassic Chambará Formation (in contrast to the black shale-rich facies of the Aramachay Formation in other areas of Peru). Examination of up to 147 m of cherty dolomite from the Aramachay Formation revealed a siliceous sponge-dominated ecosystem, including sponge body fossils, compressed in situ sponge materials, and abundant transported spiculite sediments. Siliceous sponges, mostly demosponges and rare hexactinellids, account for the chert lithology and apparently dominated the local ecology for approximately two million years. The role of metazoan biocalcifiers in sediment production and ecological structure was profoundly reduced compared to the under- and overlying formations, representing a clear ecological state shift from pre-extinction carbonate to post-extinction siliceous dominated ecosystems before the carbonate system recovered ~ 2 m.y. after the extinction.

Hettangian Jurassic Oceans Became Sponge Bob World After Triassic-Jurassic Extinction?

NEW EVIDENCE ON THE ROLE OF SILICEOUS SPONGES IN ECOLOGY AND SEDIMENTARY FACIES DEVELOPMENT IN EASTERN PANTHALASSA FOLLOWING THE TRIASSIC–JURASSIC MASS EXTINCTION

Authors:

Ritterbush et al

Abstract:

Paleoecological consequences of the global Triassic–Jurassic mass extinction (201.3 Ma) are poorly understood. Fossiliferous marine boundary records are rare, commonly condensed, and typically reveal facies changes previously attributed to eustacy. Sedimentology and biofacies analyses from stratigraphically expanded successions of the lowest Jurassic strata, New York Canyon, Nevada, were investigated with high-resolution paleoenvironmental observations, fossil surveys, and microfacies analysis. Following the collapse of the uppermost Triassic carbonate ramp, the lowest Jurassic Ferguson Hill Member of the Sunrise Formation records a midshelf habitat dominated by previously unrecognized siliceous sponges for approximately two million years. In addition, the earliest Jurassic strata from the Pucara Group, central Peruvian Andes, were examined and record a more greatly expanded stratigraphic succession of facies across the inner to middle shelf. Like Nevada, the lowest Jurassic Aramachay Formation is replete with intense concentrations of siliceous sponges. The revelation of widespread, ecologically dominant siliceous sponges has been overlooked despite detailed biofacies studies in both depositional systems. Sponges expanded across shallow environments with sparse benthic biocalcifier populations, and were likely aided by increased ocean silica concentrations from the weathering of the Central Atlantic Magmatic Province. Facies changes previously attributed to sea-level change are thus interpreted to result from the collapse of the carbonate factory concomitant with the mass extinction, with transition to an alternate state dominated by siliceous sponges before a return to carbonate platform development in the Sinemurian. Our study highlights the need to separate biofacies from paleoenvironmental analysis during mass extinction times when nonactualistic assemblages may dominate and deviate from expected environments (e.g., siliceous sponges as indicators of deep paleoenvironments).

Evidence From French Rhaetian Triassic Ichthyosaurs Experienced Severe Turnover From the Triassic-Jurassic Mass Extinction

Ichthyosaurs from the French Rhaetian indicate a severe turnover across the Triassic–Jurassic boundary

Authors:

Fischer et al

Abstract:

Mesozoic marine reptiles went through a severe turnover near the end of the Triassic. Notably, an important extinction event affected ichthyosaurs, sweeping a large part of the group. This crisis is, however, obscured by an extremely poor fossil record and is regarded as protracted over the entire Norian–earliest Jurassic interval, for the lack of a more precise scenario. The iconic whale-sized shastasaurid ichthyosaurs are regarded as early victims of this turnover, disappearing by the middle Norian. Here we evaluate the pattern of this turnover among ichthyosaurs by analysing the faunal record of two Rhaetian localities. One locality is Autun, eastern France; we rediscovered in this material the holotypes or partial ‘type’ series of Rachitrema pellati, Actiosaurus gaudryi, Ichthyosaurus rheticus, Ichthyosaurus carinatus and Plesiosaurus bibractensis; a revised taxonomic scheme is proposed. The second assemblage comes from a new locality: Cuers, southeastern France. Both these assemblages provide several lines of evidence for the presence of shastasaurid-like ichthyosaurs in the Rhaetian of Europe. These occurrences suggest that both the demise of shastasaurids and the sudden radiation of neoichthyosaurians occurred within a short time window; this turnover appears not only more abrupt but also more complex than previously postulated and adds a new facet of the end-Triassic mass extinction.

Evidence Ocean Acidification was Important to the Triassic-Jurassic Mass Extinction

The end-Triassic negative δ13C excursion: A lithologic test

Authors:

Bachan et al

Abstract:

The end-Triassic mass extinction is associated with a large negative carbon isotope excursion, which has been interpreted as reflecting the rapid injection of 13C depleted CO2 or methane associated with the emplacement of the Central Atlantic Magmatic Province. However, in a number of sections in central Europe, the negative excursion is associated with a carbonate-poor lithology, and the most isotopically depleted values are associated with the lowest percent carbonate, raising the possibility of a lithologic control on δ13Ccarb.

Here we test the uniqueness of the relationship between the carbonate-poor lithology and the δ13C signal by comparing the geochemistry of the extinction marl with two Upper Triassic carbonate-poor beds from lower positions within the same stratigraphic sections. We find that the extinction and non-extinction marls overlap nearly completely in terms of their carbonate content, but differ substantially in their isotopic trends. The extinction marl sections show strong depletions in the δ13C and δ18O of carbonate, and enrichment in δ13C of bulk organic carbon, while the non-extinction marls show almost no change in these metrics. Accordingly, the difference in isotopic content must lie in differences inherent to the beds themselves and the circumstances of their deposition and early diagenesis. Although a range of primary drivers for the isotopic trends is possible, an acidification origin for the marl, and oceanic origin for the carbon isotope excursion in carbonate are compatible with our data and supported by the broader context of the extinction.

Extraordinary Claim: Magnetic Reversals can Cause Massive Oxygen Escape, Mass Extinctions?

Oxygen escape from the Earth during geomagnetic reversals: Implications to mass extinction

Authors:

Wei et al

Abstract:

The evolution of life is affected by variations of atmospheric oxygen level and geomagnetic field intensity. Oxygen can escape into interplanetary space as ions after gaining momentum from solar wind, but Earth's strong dipole field reduces the momentum transfer efficiency and the ion outflow rate, except for the time of geomagnetic polarity reversals when the field is significantly weakened in strength and becomes Mars-like in morphology. The newest databases available for the Phanerozoic era illustrate that the reversal rate increased and the atmospheric oxygen level decreased when the marine diversity showed a gradual pattern of mass extinctions lasting millions of years. We propose that accumulated oxygen escape during an interval of increased reversal rate could have led to the catastrophic drop of oxygen level, which is known to be a cause of mass extinction. We simulated the oxygen ion escape rate for the Triassic–Jurassic event, using a modified Martian ion escape model with an input of quiet solar wind inferred from Sun-like stars. The results show that geomagnetic reversal could enhance the oxygen escape rate by 3–4 orders only if the magnetic field was extremely weak, even without consideration of space weather effects. This suggests that our hypothesis could be a possible explanation of a correlation between geomagnetic reversals and mass extinction. Therefore, if this causal relation indeed exists, it should be a “many-to-one” scenario rather the previously considered “one-to-one”, and planetary magnetic field should be much more important than previously thought for planetary habitability.

Increased SO2 Signal from Triassic-Jurassic Boundary

Increased Atmospheric SO2 Detected from Changes in Leaf Physiognomy across the Triassic–Jurassic Boundary Interval of East Greenland

Authors:

1. Karen L. Bacon (a)
2. Claire M. Belcher (b)
3. Matthew Haworth (c)
4. Jennifer C. McElwain (a)

Affiliations:

a. School of Biology and Environmental Science, University College Dublin, Belfield, Dublin, Ireland

b. College of Life and Environmental Sciences, Hatherly Laboratories, University of Exeter, Exeter, United Kingdom

c. CNR – Istituto di Biometeorologia (IBIMET), Firenze, Italy

Abstract:

The Triassic–Jurassic boundary (Tr–J; ~201 Ma) is marked by a doubling in the concentration of atmospheric CO2, rising temperatures, and ecosystem instability. This appears to have been driven by a major perturbation in the global carbon cycle due to massive volcanism in the Central Atlantic Magmatic Province. It is hypothesized that this volcanism also likely delivered sulphur dioxide (SO2) to the atmosphere. The role that SO2 may have played in leading to ecosystem instability at the time has not received much attention. To date, little direct evidence has been presented from the fossil record capable of implicating SO2 as a cause of plant extinctions at this time. In order to address this, we performed a physiognomic leaf analysis on well-preserved fossil leaves, including Ginkgoales, bennettites, and conifers from nine plant beds that span the Tr–J boundary at Astartekløft, East Greenland. The physiognomic responses of fossil taxa were compared to the leaf size and shape variations observed in nearest living equivalent taxa exposed to simulated palaeoatmospheric treatments in controlled environment chambers. The modern taxa showed a statistically significant increase in leaf roundness when fumigated with SO2. A similar increase in leaf roundness was also observed in the Tr–J fossil taxa immediately prior to a sudden decrease in their relative abundances at Astartekløft. This research reveals that increases in atmospheric SO2 can likely be traced in the fossil record by analyzing physiognomic changes in fossil leaves. A pattern of relative abundance decline following increased leaf roundness for all six fossil taxa investigated supports the hypothesis that SO2 had a significant role in Tr–J plant extinctions. This finding highlights that the role of SO2 in plant biodiversity declines across other major geological boundaries coinciding with global scale volcanism should be further explored using leaf physiognomy.

Pulsed Triassic-Jurassic Mass Extinction

Microbes, mud and methane: cause and consequence of recurrent Early Jurassic anoxia following the end-Triassic mass extinction

Authors:

1. Bas van de Schootbrugge (a)
2. Aviv Bachan (b)
3. Guillaume Suan (c)
4. Sylvain Richoz (d)
5. Jonathan L. Payne (b)


Affiliations:

a. Palaeo-environmental Dynamics Group, Institute of Geosciences, Goethe University Frankfurt, Frankfurt am Main, Germany

b. Geological and Environmental Sciences, Stanford University, Stanford, CA, USA

c. UMR, CNRS 5276, LGLTPE, Villeurbanne, France

d. Academy of Sciences, University of Graz, Graz, Austria

Abstract:

The end-Triassic mass extinction (c. 201.6 Ma) was one of the five largest mass-extinction events in the history of animal life. It was also associated with a dramatic, long-lasting change in sedimentation style along the margins of the Tethys Ocean, from generally organic-matter-poor sediments during the Triassic to generally organic-matter-rich black shales during the Jurassic. New core material from Germany provides biomarker evidence of persistent photic-zone euxinia during the Hettangian, the onset of which is associated with a series of both negative and positive carbon isotope excursions. Combined inorganic and organic geochemical and micropalaeontological analyses reveal strong similarities between the Hettangian and the better-known Toarcian anoxic event. These events appear to be the most clearly expressed events within a series of anoxic episodes that also include poorly studied black shale intervals during the Sinemurian and Pliensbachian. Both the Hettangian and Toarcian events are marked by important changes in phytoplankton assemblages from chromophyte- to chlorophyte-dominated assemblages within the European Epicontinental Seaway. Phytoplankton changes occurred in association with the establishment of photic-zone euxinia, driven by a general increase in salinity stratification and warming of surface waters. For both events, the causes of large negative carbon isotope excursions remain incompletely understood; evidence exists for both variation in the δ13C of atmospheric CO2 and variation in the sources of organic carbon. Regardless of the causes of δ13C variability, long-term ocean anoxia during the Early Jurassic can be attributed to greenhouse warming and increased nutrient delivery to the oceans triggered by flood basalt volcanism.

1.  When did the TJ Boundary move down?  That's a shift of over 1 million years.

2.  These models are relevant for the PT Extinction too.  They are NOT the same, but ofsimilar kind.  Likely the Toarcian event was of a similar kind as well.

Hettangian Isle of Skye Corals Give Insight to Post Triassic-Jurassic Mass Extinction Paleoenvironment

The Hettangian corals of the Isle of Skye (Scotland): An opportunity to better understand the palaeoenvironmental conditions during the aftermath of the Triassic – Jurassic boundary crisis

Authors:

1. M. Gretz (a)
2. B. Lathuilière (b, c)
3. R. Martini (a)
4. A. Bartolini (d)

Affiliations:

a. Department of Geology and Paleontology, University of Geneva, 13 rue des Maraîchers, 1205 Geneva, Switzerland

b. Université de Lorraine G2R, UMR 7566, Vandoeuvre-lès-Nancy, BP 239, F-54506, France

c. CNRS G2R, UMR 7566, Vandoeuvre-lès-Nancy, BP 239, F-54506, France

d. Muséum National D’Histoire Naturelle, CR2P « centre de Recherche sur la Paléodiversité et les paléoenvironnements » CNRS UMR 7207, 8 rue Buffon, 75231 Paris Cedex 05, France

Abstract:

At Ob Lusa (Isle of Skye, Scotland), six distinct coral beds were observed in a modern outcrop where a Hettangian succession is exposed. The coral associations are monogenic, belonging to Lepidophyllia, a massive cerioid genus. The lowest bed has relatively well-developed colonies that form small bioconstructions, whereas the other beds have small and dispersed colonies that are completely drowned in the matrix. Their morphology and size can vary, but the general growth fabric is dominated by platy colonies. This type of growth fabric is defined as a platestone. The most surprising characteristic of these specimens, especially for the platy corals, is their growth pattern; many samples do not exhibit the classical growth polarity because they are bifacial. Geochemical analyses (δ180, δ13C) were conducted on oyster shells that were associated with the corals. The results indicate that the mean palaeotemperature was approximately 22 °C. Sedimentological analysis revealed shallow settings where the hydrodynamic energy and siliciclastic inputs fluctuated. The general faunal assemblage of the outcrop had low diversity and was mainly composed of allochthonous bioclasts. The corals at Ob Lusa clearly did not live under ideal environmental conditions for the development of corals.

CAMP Tied to TJ Extinction Within 30K Years Radiometrically

To incriminate a global catastrophe in the extinction of a wide swath of the biosphere, you need precise dates for two events: the catastrophe—say, an asteroid impact or volcanic eruption—and the mass extinction. At the meeting, geochronologists who measure the passage of time in the steady ticking of radioactive decay presented convincing evidence that massive eruptions at the opening of the Atlantic Ocean 201 million years ago drove the mass extinction that cleared the way for the rise of the dinosaurs.

The dating—by Terrence Blackburn of the Carnegie Institution for Science in Washington, D.C., and colleagues—was impressively precise. For minerals from the end of the Triassic period, 201 million years ago, the researchers reported ages to three decimal places with a 1-sigma error of about 30,000 years, just 0.015% of the ages. That kind of precision takes careful measurements of the amounts of the radioactive element of interest and the product of its decay. That's quite a feat in mineral grains that have been ravaged for hundreds of millions of years by both the environment and their own radioactivity.

[...]

Near the end of the Triassic period, millions of cubic kilometers of magma spewed from the crack that split the supercontinent Pangaea in two and started the opening of the Atlantic Ocean. Debris from the eruptions might have chilled the climate or poisoned the environment, triggering the extinction. But previous dating had had the extinction coming before the first volcanic outburst, not at the same time.

So Blackburn and his colleagues used the latest uranium-lead techniques to date volcanic samples from seven sites on the East coast of North America and one site in Morocco. They dated the end-Triassic extinction to 201.562±0.016 million years ago (subject to change in peer review). Adding in dating of sediments surrounding eruption deposits by using astronomical cycles, they could correlate the Moroccan record to the North American record, placing the extinction at the first of three eruption pulses within the small dating errors. And those errors have gotten so small that no one is disputing that the Atlantic opening megaeruptions somehow did in enough critters to unleash the dinosaurs.

Triassic-Jurassic Boundary Extinction had Nasty, Anoxic Seas

The global mass extinction that ended the Triassic – and ushered in the Jurassic - was marked by inhospitable, sulphurous seas all around the coast, according to a new study.

While life on land seems to have been recovering, repeated poisoning of shallow seas with hydrogen sulphide knocked back the recovery of marine life during the early Jurassic. And some experts say a build-up of noxious gas could happen again.

“These coastal seas were stinking fouling seas, very unpleasant to higher life forms,” said Bas van de Schootbrugge of Goethe University Frankfurt, an author of the study published in Nature Geoscience.

[...]

Life in the Triassic world had already been decimated by catastrophic volcanic eruptions which swept in a period of high carbon dioxide levels and global warming. A fall in oxygen levels at sea and global warming led rising hydrogen sulphide levels in the shallow seas, a hotbed of marine biodiversity during this time.

“We have conclusively shown for the first time that bottom waters were strongly anoxic [low in oxygen] and rich in hydrogen sulphide directly after the mass-extinction event. Our data show that the environmental impact was of a much longer duration [than previously thought],” said van de Schootbrugge. And the lack of oxygen would have inhibited the recovery of life, prolonging the environmental misery at sea.

The scientists studied sediments from northern Germany and Luxemburg buried during at the Triassic-Jurassic boundary; they used geochemical analyses to fingerprint fossilised pigments used exclusively by green sulphur bacteria.

These bacteria live under conditions of zero oxygen but high concentrations of hydrogen sulphide. “Imagine a shallow sea where the bottom waters of up to about 20 metres under the surface are devoid of oxygen,” said Schootbrugge, describing this as bad news for corals and bivalves.

Link.  Awaiting paper.

Atmospheric CO2 Effects of the Central Atlantic Magmatic Province Eruptions

Atmospheric CO2 Effects of the Central Atlantic Magmatic Province Eruptions

1. Schaller, M. F. (a)

2. Wright, J. D. (a)

3. D. V. Kent. (a,b,*)

a. Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ, USA.

b. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA.

* To whom correspondence should be addressed. E-mail: schaller@rci.rutgers.edu

Science 331: 1404-1409. DOI: 10.1126/science.1199011

Abstract - The effects of a large igneous province on the concentration of atmospheric carbon dioxide (PCO2) are mostly unknown. In this study, we estimate PCO2 from stable isotopic values of pedogenic carbonates interbedded with volcanics of the Central Atlantic Magmatic Province (CAMP) in the Newark Basin, eastern North America. We find pre-CAMP PCO2 values of ~2000 parts per million (ppm), increasing to ~4400 ppm immediately after the first volcanic unit, followed by a steady decrease toward pre-eruptive levels over the subsequent 300 thousand years, a pattern that is repeated after the second and third flow units. We interpret each PCO2 increase as a direct response to magmatic activity (primary outgassing or contact metamorphism). The systematic decreases in PCO2 after each magmatic episode probably reflect consumption of atmospheric CO2 by weathering of silicates, stimulated by fresh CAMP volcanics.

Anyone have a copy? Again, LBNL doesn't subscribe to Science.

Hattip Chinleana.

Vulcanism and the Late Triassic Mass Extinction

Compound-specific carbon isotopes from Earth’s largest flood basalt eruptions directly linked to the end-Triassic mass extinction

1. Jessica H. Whiteside (a,1)
2. Paul E. Olsen (b,1)
3. Timothy Eglinton (c)
4. Michael E. Brookfield (d)
5. Raymond N. Sambrotto (e)


a. Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912;

b. Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964;

c. Department of Marine Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543;

d. Institute of Earth Sciences Academia Sinica, Nankang, Taipei 11529, Taiwan; and

e. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964

1. To whom correspondence may be addressed. E-mail: Jessica_Whiteside@Brown.edu or polsen@ldeo.columbia.edu.


Abstract:

A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused by eruptions of continental flood basalt provinces. However, the necessary serial relationship between these eruptions, isotopic excursions, and extinctions has never been tested in geological sections preserving all three records. The end-Triassic extinction (ETE) at 201.4 Ma is among the largest of these extinctions and is tied to a large negative carbon isotope excursion, reflecting perturbations of the carbon cycle including a transient increase in CO2. The cause of the ETE has been inferred to be the eruption of the giant Central Atlantic magmatic province (CAMP). Here, we show that carbon isotopes of leaf wax derived lipids (n-alkanes), wood, and total organic carbon from two orbitally paced lacustrine sections interbedded with the CAMP in eastern North America show similar excursions to those seen in the mostly marine St. Audrie’s Bay section in England. Based on these results, the ETE began synchronously in marine and terrestrial environments slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco, a CO2 super greenhouse, and marine biocalcification crisis. Because the temporal relationship between CAMP eruptions, mass extinction, and the carbon isotopic excursions are shown in the same place, this is the strongest case for a volcanic cause of a mass extinction to date.

And the commentary from Rampino.

Could someone send these to me? For some reason the Lab has lost its subscription to PNAS, of all goofy things.

anzha el-why-you at gmail dot com.

thanx.

CO2 Linked to TJ Extinction

Scientists have unearthed striking evidence for a sudden ancient collapse in plant biodiversity. A trove of 200 million-year-old fossil leaves collected in East Greenland tells the story, carrying its message across time to us today.

Results of the research appear in this week's issue of the journal Science.

The researchers were surprised to find that a likely candidate responsible for the loss of plant life was a small rise in the greenhouse gas carbon dioxide, which caused Earth's temperature to rise.

Global warming has long been considered as the culprit for extinctions--the surprise is that much less carbon dioxide gas in the atmosphere may be needed to drive an ecosystem beyond its tipping point than previously thought.

"Earth's deep time climate history reveals startling discoveries that shake the foundations of our knowledge and understanding of climate change in modern times," says H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which partially funded the research.

Jennifer McElwain of University College Dublin, the paper's lead author, cautions that sulfur dioxide from extensive volcanic emissions may also have played a role in driving the plant extinctions.

"We have no current way of detecting changes in sulfur dioxide in the past, so it's difficult to evaluate whether sulfur dioxide, in addition to a rise in carbon dioxide, influenced this pattern of extinction," says McElwain.

The time interval under study, at the boundary of the Triassic and Jurassic periods, has long been known for its plant and animal extinctions.

[...]

The paper, "Fossil Plant Relative Abundances Indicate Sudden Loss of Late Triassic Biodiversity in East Greenland," was co-authored by McElwain, Wagner and Stephen Hesselbo of the University of Oxford in the U.K.

Paper, Please!

This is sounding more and more like the Permian Extinction Model. I'll write more as I have time. I still need to write up Dr Wignall's Guadelupean Mass Extinction paper. Oy.

Paleo Marine Invertebrate Diversity Rise Less Explosive Than Thought

Diversity among the ancestors of such marine creatures as clams, sand dollars and lobsters showed only a modest rise beginning 144 million years ago with no clear trend afterwards, according to an international team of researchers. This contradicts previous work showing dramatic increases beginning 248 million years ago and may shed light on future diversity.

"Some of the time periods in the past are analogies for what is happening today from global warming," says Jocelyn Sessa, doctoral candidate in geosciences, Penn State. "Understanding what happened with diversity in the past can help us provide some prediction on how modern organisms will fare. If we know where we have been, we know something about where it will go."

Using contemporary statistical methods and the Paleobiology Database, the researchers report, in today's (July 4) issue of Science, a new diversity curve that shows that most of the early spread of invertebrates took place well before the Late Cretaceous, and that the net increase through the period since, is proportionately small relative to the 65 million years that elapsed.

One key to the new curve is the Paleobiology Database, (http://paleodb.org) housed at the National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara. Previous research was based on databases of marine invertebrate fossils that recorded only the first occurrence of an organism and the last occurrence of the organism. There was no information in between for the organism.

"Over 30 years ago, researchers looked at the curve they had and considered that perhaps diversity did not increase at all," says Mark E. Patzkowsky, associate professor of geosciences. "What researchers saw was the diversity curve leveled off for quite some time and then took off exponentially. However, diversity results are strongly controlled by sampling techniques."

The new database allows researchers to standardize sample size because it includes multiple occurrences of each fossil. Researchers can randomly choose equal samples from equal time spans to create their diversity curve. This new curve uses 11 million-year segments, but the researchers hope to reduce the time intervals to 5 million years to match the interval of the previous curve, known as Sepkoski.

The data for this study contains 284,816 fossil occurrences of 18,702 genera that equals about 3.4 million specimens from 5384 literature sources. The old curve, developed by J. John Sepkoski Jr., used a database that contained only about 60,000 occurrences.

The researchers also looked at evenness in diversity. If there are 100 specimens divided into 10 time intervals, they could be divided with 10 individual specimens in each interval; or 91 specimens could be in one interval with one each in the remainder. The more even the distribution, the higher the evenness.

"Evenness says something about resource distribution," says Patzkowsky. "Much of invertebrate diversity has been attributed to diversity increase in the tropics, but the curve is not driven by that totally. It seems that 450 million years ago was not so different from today because it also contained more diversity in the tropics."

The major points of the Sepkoski curve are still seen in the new curve. Some things that are not seen, such as the decrease in diversity due to the Cretaceous Tertiary (KT) extinction 65 million years ago are not visible because of the scale of the intervals used. The extinction and recovery in the KT took less than 11 million years and so do not show. Some things not seen on the Sepkoski curve include a peak in the Permian. Also unexpected is that the diversity in the Jurassic (206 to 144 million years ago) is lower than diversity in the Triassic (248 to 206 million years ago), indicating a dip and rise in the diversity curve. The curve then rises in the Cretaceous and remains more or less flat after that. The previously thought exponential increase in diversity is not there.

Interesting. The Jurassic might have had less diversity than the Triassic which was recovering from the PT Extinction (and took a long time to do so).

I have a feeling that how you sample this greatly influences the results and I am sure that there are some nontrivial bits of clean up that need to happen as far as naming in the database. I've encountered this allegation a nontrivial number of times while reading on mass extinctions and the Sepkoski database.