Evidence of Extensive Mercury Pollution During Permian Triassic Mass Extinction

Isotopic signatures of mercury contamination in latest Permian oceans

Authors:

Grasby et al

Abstract:

Sedimentary records from the northwest margin of Pangea and the Tethys show anomalously high Hg levels at the latest Permian extinction boundary. Background δ202Hg values are consistent with normal marine conditions but exhibit negative shifts coincident with increased Hg concentrations. Hg isotope mass-independent fractionation (Δ199Hg) trends are consistent with volcanic input in deep-water marine environments. In contrast, nearshore environments have Δ199Hg signatures consistent with enhanced soil and/or biomass input. We hypothesize that the deep-water signature represents an overall global increase in volcanic Hg input and that this isotope signature is overwhelmed in nearshore locations due to Hg from terrestrial sources. High-productivity nearshore regions may have experienced stressed marine ecosystems due to enhanced Hg loading.

Periodicity AGAIN?!?! Dark Matter 'Caused' Mass Extinctions?

Mass Extinctions and a Dark Disk

Authors:

Kramer et al

Abstract:

We consider whether the observed periodicity of mass extinctions and of comet impacts on Earth is consistent with Solar oscillation about the Galactic midplane and spiral arm crossings. It is of further interest to determine whether a hypothetical thin dark disk is necessary to give the right periodicity, and whether such a dark disk is allowed given kinematic and other observational constaints on the Galaxy's gravitational potential. We show that a dark disk consistent with recent bounds, combined with data for spiral arm crossing, can lead to the required periodicity. Moreover, we find that the best fit values correctly predict the date of the Chicxulub crater dated to 66 My ago.

Permian Extinction NOT as Deadly as Originally Thought?

Estimates of the magnitudes of major marine mass extinctions in earth history

Author:

Stanley

Abstract:

Procedures introduced here make it possible, first, to show that background (piecemeal) extinction is recorded throughout geologic stages and substages (not all extinction has occurred suddenly at the ends of such intervals); second, to separate out background extinction from mass extinction for a major crisis in earth history; and third, to correct for clustering of extinctions when using the rarefaction method to estimate the percentage of species lost in a mass extinction. Also presented here is a method for estimating the magnitude of the Signor–Lipps effect, which is the incorrect assignment of extinctions that occurred during a crisis to an interval preceding the crisis because of the incompleteness of the fossil record. Estimates for the magnitudes of mass extinctions presented here are in most cases lower than those previously published. They indicate that only ∼81% of marine species died out in the great terminal Permian crisis, whereas levels of 90–96% have frequently been quoted in the literature. Calculations of the latter numbers were incorrectly based on combined data for the Middle and Late Permian mass extinctions. About 90 orders and more than 220 families of marine animals survived the terminal Permian crisis, and they embodied an enormous amount of morphological, physiological, and ecological diversity. Life did not nearly disappear at the end of the Permian, as has often been claimed.

Evidence Ediacaran Biota Members Survived Into the Cambrian

Transitional Ediacaran–Cambrian small skeletal fossil assemblages from South China and Kazakhstan: Implications for chronostratigraphy and metazoan evolution

Authors:

Yang et al

Abstract:

The Ediacaran–Cambrian transition records distinct evolutionary changes of metazoans. The Ediacaran fossils (i.e., Ediacara-type biota and tubular fossils) are contrasting with the diverse small skeletal fossils (SSFs) from the early Cambrian. The apparent dissimilarities hindered studies deciphering their evolutionary relationships. This also led to a popular assumption that there exists a mass extinction of the Ediacara biota and cloudinids at the Precambrian–Cambrian (Pc–C) boundary. Here we report for the first time a transitional fauna which consists of typical elements of Ediacaran, i.e. cloudinids and related tubicolous organisms, together with Cambrian SSFs including protoconodonts, anabaritids and siphogonuchitids from South China and Maly Karatau (Kazakhstan). The sediments yielding the transitional fauna are characterized by siliceous rocks in both regions and were previously considered to be unfossiliferous. Their chronostratigraphic assignment in South China has been debated for years. Based on the new fossil assemblage, the siliceous strata of the Daibu Member (Northeast Yunnan, South China) and the basal Kuanchuanpu Formation (South Shaanxi, South China) can be assigned to the earliest Cambrian SSF biozone (Anabarites trisulcatus–Protohertzina anabarica Assemblage Zone) and thus can be considered of early Cambrian in age. A new subzone of the earliest SSF zone in eastern Yunnan (South China) is proposed herein defined as Ganloudina symmetrica–Rugatotheca typica Interval Subzone. The new fauna demonstrates that the cloudinids, originally confined to the late Ediacaran, persisted into the Cambrian Fortunian, and no major extinction event occurred at the Pc–C transition.

Evidence of an End Ediacaran Paleoenvironmental Disturbance

The end of the Ediacaran: Two new exceptionally preserved body fossil assemblages from Mount Dunfee, Nevada, USA

Authors:

Smith et al

Abstract:

Evaluation of hypotheses that relate environmental to evolutionary change across the Ediacaran-Cambrian transition has been hampered by a dearth of sections that preserve both the last appearance of Ediacaran body fossils and the first appearance of Treptichnus pedum within carbonate-rich strata suitable for chemostratigraphic studies. Here, we report two new exceptionally preserved latest Ediacaran fossil assemblages from the Deep Spring Formation at Mount Dunfee, Nevada (USA). Further, we report these occurrences in a high-resolution carbon isotope chemostratigraphic framework, permitting correlation on a regional and global scale. The lower of the two horizons, at the base of the Deep Spring Formation, hosts a body fossil assemblage that includes Gaojiashania, other vermiform body fossils, and possible Wutubus annularis interbedded with Cloudina shell beds. The upper of the two fossil horizons, in the Esmeralda Member of the Deep Spring Formation, contains Conotubus and occurs within the basal Cambrian negative carbon isotope excursion, establishing it as the youngest Ediacaran fossil assemblage discovered to date. This is the first report of Gaojiashania, Conotubus, and Wutubus in Laurentia, extending the known stratigraphic ranges and biogeographic distributions of these taxa to a global scale. These data refine the relative ages of defining characteristics of the Ediacaran-Cambrian boundary and confirm that a large perturbation to the carbon cycle and surface ocean conditions coincided with the extinction of Ediacaran organisms.

A Major Floral Extinction 500,000 Years After the Permian-Triassic Mass Extinction (Another Pulse?)

There have been several mass extinctions in the history of Earth with adverse consequences for the environment. Researchers from the University of Zurich have now uncovered another disaster that took place around 250 million years ago and completely changed the prevalent vegetation during the Lower Triassic.

There have been several mass extinctions in the history of Earth. One of the largest known disasters occurred around 252 million years ago at the boundary between the Permian and the Triassic. Almost all sea-dwelling species and two thirds of all reptiles and amphibians died out. Although there were also brief declines in diversity in the plant world, they recovered in the space of a few thousand years, which meant that similar conditions to before prevailed again.

link.

90% of North American Mammals Estimated to Have Died out Because of the Dinosaur Killer

Over 90 per cent of mammal species were wiped out by the same asteroid that killed the dinosaurs in the Cretaceous period 66 million years ago, significantly more than previously thought.

A study by researchers at the Milner Centre for Evolution at the University of Bath and published in the Journal of Evolutionary Biology, reviewed all mammal species known from the end of the Cretaceous period in North America. Their results showed that over 93 per cent became extinct across the Cretaceous-Paleogene (K-Pg) boundary, but that they also recovered far more quickly than previously thought.

The scientists analysed the published fossil record from western North America from two million years before the Cretaceous-Paleogene boundary, until 300,000 years after the asteroid hit. They compared species diversity before and after this extinction event to estimate the severity of the event and how quickly the mammals recovered. The extinction rates were much higher than previous estimates based on more limited data sets.

Dr Nick Longrich from the Milner Centre for Evolution, in the University of Bath's Department for Biology & Biochemistry, explained: "The species that are most vulnerable to extinction are the rare ones, and because they are rare, their fossils are less likely to be found. The species that tend to survive are more common, so we tend to find them.

link.

The Antarctic was NOT a Refuge From the KT/K-Pg Mass Extinction

A study of more than 6,000 marine fossils from the Antarctic shows that the mass extinction event that killed the dinosaurs was sudden and just as deadly to life in the polar regions.

Previously, scientists had thought that creatures living in the southernmost regions of the planet would have been in a less perilous position during the mass extinction event than those elsewhere on Earth.

The research, published today in the journal Nature Communications, involved a six-year process of identifying more than 6,000 marine fossils ranging in age from 69- to 65-million-years-old that were excavated by scientists from the University of Leeds and the British Antarctic Survey on Seymour Island in the Antarctic Peninsula.

link.

Helms Deep for Metazoan Reef Builders Found From Permian Extinction era Slovenia?

Equatorial Palaeotethys as the last sanctuary for late Permian metazoan reef-builders: New evidence from the Bellerophon Formation of Slovenia

Authors:

Sremac et al

Abstract:

The rise and demise of warm-temperate Permian reefs and biostromes reflect the complex geologic history of this dynamic period. Environments suitable for reef-builders were devastated by the Guadalupian/Lopingian crisis, and Lopingian reefs have only been recorded at a small number of localities. The uppermost Permian limestones of the Bellerophon Formation, on the Vojsko Plateau (Slovenia), contain small, lenticular biostromes within a bioclastic wackestone/packstone lithofacies. The major biostrome builders are medium-sized coralline sponges (Demospongea and Calcarea), encrusted by smaller sponges, tube worms, sessile foraminifera, calcareous algae (Archaeolithoporella) and Shamovella (i.e., Tubiphytes), all of which are typically covered by microbial crusts. The biostromes are characteristically composed of bafflestone and bindstone, incorporating sporadic framestone. Narrow belts of floatstone surround the buildups, and sponge debris is also present in lenses within the mud matrix between metazoan bafflestones. The fossils are generally well-preserved, although the fine skeletal microstructure has been partially recrystallized. Sponges are heavily calcified, and ontogenic thickening of the skeleton can be observed in some encrusters. Framboidal pyrite, forming thin films on the inner walls of sponge chambers, suggests the presence of sulphate-reducing bacteria. These microbial symbionts may have enabled the sponges to survive in the anoxic marine environments of the uppermost Permian. The Changshingian sponge biostromes of the Vojsko Plateau represent the westernmost known occurrence of contemporary metazoan boundstones in the Palaeotethys.

Carbon cycle history across the Jurassic–Cretaceous boundary

Carbon cycle history through the Jurassic–Cretaceous boundary: A new global δ13C stack

Authors:

Price et al

Abstract:

We present new carbon and oxygen isotope curves from sections in the Bakony Mts. (Hungary), constrained by biostratigraphy and magnetostratigraphy in order to evaluate whether carbon isotopes can provide a tool to help establish and correlate the last system boundary remaining undefined in the Phanerozoic as well provide data to better understand the carbon cycle history and environmental drivers during the Jurassic–Cretaceous interval. We observe a gentle decrease in carbon isotope values through the Late Jurassic. A pronounced shift to more positive carbon isotope values does not occur until the Valanginian, corresponding to the Weissert event. In order to place the newly obtained stable isotope data into a global context, we compiled 31 published and stratigraphically constrained carbon isotope records from the Pacific, Tethyan, Atlantic, and Boreal realms, to produce a new global δ13C stack for the Late Oxfordian through Early Hauterivian interval. Our new data from Hungary is consistent with the global δ13C stack. The stack reveals a steady but slow decrease in carbon isotope values until the Early Valanginian. In comparison, the Late Jurassic–Early Cretaceous δ13C curve in GTS 2012 shows no slope and little variation. Aside from the well-defined Valanginian positive excursion, chemostratigraphic correlation durSchning the Jurassic–Cretaceous boundary interval is difficult, due to relatively stable δ13C values, compounded by a slope which is too slight. There is no clear isotopic marker event for the system boundary. The long-term gradual change towards more negative carbon isotope values through the Jurassic–Cretaceous transition has previously been explained by increasingly oligotrophic condition and lessened primary production. However, this contradicts the reported increase in 87Sr/86Sr ratios suggesting intensification of weathering (and a decreasing contribution of non-radiogenic hydrothermal Sr) and presumably a concomitant rise in nutrient input into the oceans. The concomitant rise of modern phytoplankton groups (dinoflagellates and coccolithophores) would have also led to increased primary productivity, making the negative carbon isotope trend even more notable. We suggest that gradual oceanographic changes, more effective connections and mixing between the Tethys, Atlantic and Pacific Oceans, would have promoted a shift towards enhanced burial of isotopically heavy carbonate carbon and effective recycling of isotopically light organic matter. These processes account for the observed long-term trend, interrupted only by the Weissert event in the Valanginian.

Verbebrate Coprolites Became Less Diverse During the Permian/Triassic Extinction

Reduction of vertebrate coprolite diversity associated with the end-Permian extinction event in Vyazniki region, European Russia

Authors:

Niedźwiedzki et al

Abstract:

This study investigates the paleoecological significance of vertebrate coprolites collected from seven sections and three lithofacies of the uppermost Permian and lowermost Triassic succession from the Vyazniki site in the European part of Russia. The analysed specimens (coprolites and possibly some cololites) were grouped into nine morphotypes (A–I).The coprolite morphotypes were characterized geochemically and compared to the record of other Permian and Triassic coprolites worldwide. Based on the stratigraphic position, shape, structure and composition, all morphotypes were linked to supposed producers. The phosphatic composition of most of the morphotypes and inclusions of arthropod remains, fish scales and bone fragments, suggest that they were produced by carnivores, but non-phosphatic, carbonate-rich, large and oval-shaped coprolites with impressions after plant remains have also been found. The extinction of terrestrial vertebrates around the Permian–Triassic boundary in Russia is interpreted to have occurred within a few thousands of years. Here, we show a pattern of coprolite morphotypes disappearing across this boundary that is consistent with a relatively sudden change in the vertebrate faunal composition across this interval.

The End of All Things #3

Cretaceous-Paleogene (K-Pg/KT) Mass Extinction:

The Chicxulub Impact Crater will be drilled. Some are saying for the first time, but I do believe the original oil workers who reported it back in the 80s (?) did so before.

There was a partial collapse of the marine carbon pump at the K-Pg boundary.marine

Permian Triassic Mass Extinction:

There is contrary evidence from conondont tooth oxygen isotopes suggesting a sharp temperature drop right at the PT Extinction. This is contrary to the global cooking scenario.

The Permian ocean bottom waters in China were not anoxic at the time of the PT Extinction.

In South China, the redox conditions were fluctuating at the PT Boundary.

The Kayitou Formation in China appears to have the terrestrial record of the PT Extinction.

There is also evidence of cyanobacteria blooms from China as well across the PT.

Devonian Mass Extinctions:

Here's evidence of what happened during the Famenian-Frasnian Event (aka mass extinction) in Devonian in China.

There was a disruption in the nitrogen cycle at the end Devonian Mass Extinction.

Here's some more interesting evidence of what was going on during the end Devonian Mass Extinction.

The End of All Things #2

General:

What was the impact of mass extinctions on tetrapod diversity?

Paleozoic:

Permian Triassic Mass Extinction:

Is the Lilliput Effect real and universal during the PT Extinction?

The anoxic conditions of the Permian Extinction's oceans held back life's recovery for a long time into the Triassic.

The Permian-Triassic boundary has been found in Germany.

It was proposed that drought helped caused mass die offs at the PT Extinction.  Some of the evidence is disputed.

Mesozoic:

Toarcian Jurassic Mass Extinction:

What were the impacts of the Toarcian extinction in the oceans?

Jurassic Cretaceous Transition (tithonian mass extinction?)

There is evidence of a strong turnover at the JC Boundary, potentially a mass extinction.

Lower Cretaceous mass extinction:

The lower Cretaceous ocean seems to have gone through a unique event, being anoxic without producing black shales.
 
Cenozoic:

Sixth Mass Extinction:

Humans are causing an acceleration in evolution by wiping out the youngest species.

The University of York has compiled an biological history of the extinction of megafauna on the island of Zanzibar.

People wiped out a tiny island deer in Panama.

Placental Mammals Exploded in Diversity After the KT/K-Pg Mass Extinction

Resolving the relationships of Paleocene placental mammals

Authors:

Halliday et al

Abstract:

The ‘Age of Mammals’ began in the Paleocene epoch, the 10 million year interval immediately following the Cretaceous–Palaeogene mass extinction. The apparently rapid shift in mammalian ecomorphs from small, largely insectivorous forms to many small-to-large-bodied, diverse taxa has driven a hypothesis that the end-Cretaceous heralded an adaptive radiation in placental mammal evolution. However, the affinities of most Paleocene mammals have remained unresolved, despite significant advances in understanding the relationships of the extant orders, hindering efforts to reconstruct robustly the origin and early evolution of placental mammals. Here we present the largest cladistic analysis of Paleocene placentals to date, from a data matrix including 177 taxa (130 of which are Palaeogene) and 680 morphological characters. We improve the resolution of the relationships of several enigmatic Paleocene clades, including families of ‘condylarths’. Protungulatum is resolved as a stem eutherian, meaning that no crown-placental mammal unambiguously pre-dates the Cretaceous–Palaeogene boundary. Our results support an Atlantogenata–Boreoeutheria split at the root of crown Placentalia, the presence of phenacodontids as closest relatives of Perissodactyla, the validity of Euungulata, and the placement of Arctocyonidae close to Carnivora. Periptychidae and Pantodonta are resolved as sister taxa, Leptictida and Cimolestidae are found to be stem eutherians, and Hyopsodontidae is highly polyphyletic. The inclusion of Paleocene taxa in a placental phylogeny alters interpretations of relationships and key events in mammalian evolutionary history. Paleocene mammals are an essential source of data for understanding fully the biotic dynamics associated with the end-Cretaceous mass extinction. The relationships presented here mark a critical first step towards accurate reconstruction of this important interval in the evolution of the modern fauna.

Academic Bun Fight! Upper Triassic Cotham Marble is NOT Evidence of a Mass Extinction

That was NOT a sign!

COMMENT TO IBARRA ET AL. MICROFACIES OF THE COTHAM MARBLE: A TUBESTONE MICROBIALITE FROM THE UPPER TRIASSIC, SOUTHWESTERN U.K

Authors:

Mayall et al

Abstract:

Ibarra et al. (2014) have presented an interesting paper on the Cotham Marble, an enigmatic microbialite from the Rhaetian Penarth Group of SW England, and an iconic piece of British stratigraphy. They have re-interpreted some aspects of our earlier work (Wright and Mayall 1981) in which we tried to be amongst the first researchers to apply an ethological approach to decipher an ancient microbial texture. That paper (Wright and Mayall 1981) was restricted editorially with respect to its content requiring a second one to illustrate the microbial microtextures we felt were critical to understanding the morphogenesis of the limestone (Mayall and Wright 1981). In addition to challenging previously published work, Ibarra et al. (2014) use the Cotham Marble to identify evidence for the late Triassic mass extinction event, thus substantially broadening the importance of this unit for the wider readership. However we would like to take this opportunity to question a number of their conclusions, in particular using the Cotham Marble as an indicator of a mass extinction event and the role of Microtubus communis in forming the Cotham Marble.

Yes, it is!

MICROFACIES OF THE COTHAM MARBLE: A TUBESTONE CARBONATE MICROBIALITE FROM THE UPPER TRIASSIC SOUTHWESTERN U.K.: A REPLY

Authors:

Ibarra et al

Abstract:

Mayall and Wright question interpretations in our microfacies analysis of the Cotham Marble microbialites (Ibarra et al. 2014) in which we primarily highlight previously overlooked aspects of Cotham Marble microbialite formation. They are specifically unconvinced about the Cotham Marble’s potential relevance to the end-Triassic mass extinction and our interpretation that Microtubus is not integral to the formation of the dendrolitic microbialite phases. Here we address Mayall and Wright’s comments under the same headings in which they present them.

Dr Gerta Keller Trumpets a Charge: Multiple Papers About Deccan Traps and the the K-Pg/KT Mass Extinction

Dr Keller has been leading an insurgency against the idea the Chicxulub impact was the underlying event that brought about the Cretaceous-Paleogene (K-Pg) Mass Extinction (formerly the KT Extinction).  This is rather contrarian to the generally accepted theory.  

The journal Paleaeogeography, Palaeoclimateology, Palaeoecology has an issue dedicated to how volcanic eruptions impacted (see what I did there?) past mass extinctions (or didn't as it may be).  That's the reason for all the volcano related posts this past week.  

Dr Keller's 'team' has a large number of articles in the publication.  Rather than do my traditional one-paper-per-post method, I am going to do a list here of each.  The reason being I don't buy her hypothesis that the Deccan Traps caused the mass extinction during the Maastrichtian.  I've posted as much since the evidence comparing mass extinctions already strongly tied to volcanic eruptions is rather different from what is present for the K-Pg Extinction.  I wrote as much in the Stop Dreaming post.  

That said, I am sure the Deccan Traps did cause some environmental impacts (see!), but they are insufficient to have caused the mass extinction.

While I admire tenacity, I think she has crossed over to religion.  However, rather than ignoring the recent papers, since they are peer reviewed papers in a respected journal, I am going to link to each here with a very short title and a description of each and a short comment.

Upheavals during the Late Maastrichtian: Volcanism, climate and faunal events preceding the end-Cretaceous mass extinction. Keller et al present their case the Maastrichtian Cretaceous was a time a climate upheaval and ecological degradation caused by the Deccan Traps with the ecology dominated by opportunistic, disaster taxa.  My comment: T rex.  Too big.

A multi-proxy approach to decode the end-Cretaceous mass extinction. Punekar argues there are multiple bits of evidence suggest the Deccan Traps caused the mass extinction at the K-Pg, especially the release of 12 to 28 teratons of carbon. Comment: Unfortunately, in the same journal edition, the OAE1 from the Early Aptian Cretaceous is stated to have been caused by the release of 20 teratons of carbon. The OAE1 was a mass extinction but a very, very mild one. Additionally, in a surprise result, calciferous plankton actually grow MORE with higher carbon dioxide levels, not less as was expected.

Tracing acidification induced by Deccan Phase 2 volcanism. Font et al ID some potential evidence of aquatic acidification at the end of the Deccan 2 Eruptions. These are located in India. Comment: Best to check to see how global this was before making a claim of global occurrence.

Palaeoenvironmental changes associated with Deccan volcanism, examples from terrestrial deposits from Central India. Fantasia et al present evidence of local impacts of the Deccan Traps caused stressed environment from India. Their claim is the DT caused environmental stress and could have made the Maastrichtian fauna vulnerable to a mass extinction at the end of the Cretaceous. Comment: Possible, but this could be completely local. Mount ST Helens did enormous damage locally, but only modestly globally.

Climatic fluctuations and sea-surface water circulation patterns at the end of the Cretaceous era: Calcareous nannofossil evidence. Thibault et al make the argument surface plankton became stressed and lost species during the proposed Deccan Warmings. However, 100k to 140k years before the K-Pg Boundary, the plankton had regained their species richness. Comment: Interesting. Given the problems of IDing what forminifers are what species I'd be cautious. The recovery would suggest whatever stress caused by the DTs had ended though.

Siberian Traps Released a Large Amount of Halogen Gases During Eruption, Contributed to Mass Extinction

The basalt pipes of the Tunguska Basin (Siberia, Russia): High temperature processes and volatile degassing into the end-Permian atmosphere

Authors:

Polozlov et al

Abstract:

A number of mechanisms have been proposed to explain the end-Permian crisis. Many of them explore the link between this catastrophe and the Siberian Traps. We test the hypothesis that eruption of thermogenic gas generated in contact aureoles around igneous sills intruded into evaporite sequences of the Tunguska Basin triggered the crisis. In particular, we test the idea that the aspect that breccia pipes represent conduits for voluminous gas migration from the deep basins to the atmosphere. This contribution sheds new light on the pipe formation based on new field and borehole observations and electron microscopy analyses. Of more than three hundred mapped magnetite-bearing basalt pipes, 43 are classified as diatremes. The diatremes are usually circular or elliptical, with multiple zones of brecciation reaching the surface, sometimes with preserved in-filled crater lakes. The pipe diameter on the surface varies from a few tens of meters for small single diatremes to about a kilometer. The largest crater lake area is 2.7 km2. We have conducted a detailed study of the breccias in the Sholokhovsk basalt pipe located within the Nepa potash deposit in the Tunguska Basin, Siberia, Russia (about N 59° and E 107°) and find that the breccias are cemented by carbonate matrix (calcite, dolomite) and halite. Breccia clasts are altered at various temperatures, evidenced by growth of albite and garnet from basaltic glass, and diopside, garnet, magnetite and chlorine-bearing amphibole (up to 1.8% Cl) in altered magmatic clasts. These mineral assemblages suggest high temperature interactions with evaporites within the pipe conduits. The large number of pipes support that degassing of halogen-rich volatiles was a widespread and violent process with implications for the end-Permian crisis.

Did a Magma Injection Into Organic Sediments at the Barremian/Aptian Boundary Release Carbon Gases, Trigger Oceanic Anoxic Event 1a?

The Early Cretaceous Barents Sea Sill Complex: Distribution, 40Ar/39Ar geochronology, and implications for carbon gas formation

Authors:

Ploteau et al

Abstract:

Mafic igneous rocks of Cretaceous age (80–130 Ma) scattered around the Arctic Ocean are commonly referred to as the High Arctic Large Igneous Province (HALIP). We have mapped out the distribution of HALIP igneous rocks in the Barents Sea region over the past decade based on integrated seismic–gravity–magnetic interpretation, field work, review of publications, and analyses of new and vintage borehole and field samples. The mapping reveals abundant igneous rocks in the northern and eastern Barents Sea covering an area of ~ 900,000 km2 with a conservative volume estimate of 100,000 to 200,000 km3 of intrusions. The igneous province is dominated by sheet intrusions injected into Triassic and Permian sedimentary rocks. Hydrothermal vent complexes are rare, and only two potential vent complexes have been identified on seismic data in the eastern Barents Sea. We have further done extensive radiometric dating of the igneous samples in the Barents Sea region. New 40Ar/39Ar dating of thirteen samples from Svalbard reveal ages of crystallization and alteration. The large age span (60–140 Ma for the raw ages) is likely due to partial or complete overprint of the K/Ar system in plagioclase, and the age of the magma emplacement is better represented by U/Pb TIMS ages. Only one of our 40Ar/39Ar analyses of plagioclase yielded a statistically valid age that is in line with the recently published U/Pb TIMS ages of 122–125 Ma. The new data clearly document that relying on published data from the K/Ar system can lead to erroneous conclusions on the age of crystallization in this province without a careful use of additional 40Ar/39Ar degassing data (i.e., K/Ca). We propose that the magmatism on Svalbard and Franz Josef Land represents a distinct magmatic event near the Barremian/Aptian boundary (125 Ma) in the Barents Sea. This Early Cretaceous Barents Sea magmatism resulted in the formation of the BSSC (Barents Sea Sill Complex). BSSC age rocks are also present in Arctic Canada (Sverdrup Basin) and on Bennett Island (New Siberia Islands). The massive injection of hot magma into potentially organic-rich sediments in the eastern and northern Barents Basin caused rapid organic matter maturation and formation of thermogenic gas and oil in contact aureoles. We estimate that up to 20,000 Gt of carbon were potentially mobilized, corresponding to 175 trillion barrels of oil equivalent. The production rates and fate of the carbon gases are uncertain. However, we speculate that rapid release of aureole greenhouse gases (methane) may have triggered the Oceanic Anoxic Event 1a (OAE1a) and the associated negative δ13C excursion in the Early Aptian. Some of the methane may also be trapped in the vast hydrocarbon gas accumulations found in the east Barents Basin.

Did the Siberian Traps Begin With an Ooze or a Bang?

The onset of flood volcanism in the north-western part of the Siberian Traps: Explosive volcanism versus effusive lava flows

Authors:

Jerram et al

Abstract:

The Siberian Traps large igneous province was formed during the end-Permian, about 252 Ma ago. Basaltic melt was injected into the organic and salt rich Tunguska sedimentary basin, forming interconnected sill complexes and associated hydrothermal vent complexes. Thick deposits of basaltic tuff and tephra covered the paleosurface before the onset of flood volcanism, commonly taken as direct evidence for the explosive nature of the initial phase of volcanism. The field work in this study revealed that tuffs are virtually absent along a 150 km long transect along the Dyupkun lake and Kureika river, even though tuff is shown on available geological maps. Towards the south and west, the transition between the end-Permian sediments and the flood basalts is either characterized by thin (2–5 m) to no tephra deposits (Khantaika area), hyaloclastites and associated lake-deposited tephra (Kureika area), or massive tephra deposits from local eruptive centers (Severnaya area). The new results can be put into the context of other studies about volcanic tuff horizons in Siberia, and questions the notion of province-scale explosive volcanism in Siberia during the onset of flood volcanism. Moreover, the main thicknesses of explosive tuff deposits, up to 700 m, are located in the central and southern parts of the province where the LIP erupted through thick Cambrian salt and carbonate sequences. Since numerous phreatomagmatic pipes are present in these areas, we suggest a causal relationship between deep magma–sediment interactions, explosive eruptions and the resulting environmental stress that initiated the end-Permian mass extinction.

YAGUMETs! Flood Basalt Eruptions Mass Extinction Impacts are Depend on WHERE the Eruption Takes Place

The effects of large igneous provinces on the global carbon and sulphur cycles

Authors:

Jones et al

Abstract:

The correlation between large igneous provinces (LIPs), extinction events, and rapid climate change suggests that volcanism can have a detrimental impact on Earth surface conditions. Changes in atmospheric and ocean chemistry, particularly the climate-sensitive carbon and sulphur cycles, are among the most probable processes for inducing global environmental stress. However, the interactions and feedbacks between volcanism and these cycles are numerous and complex, making the characterisation of the response to a LIP challenging. Here we summarise the sources and sinks of carbon and sulphur from large scale volcanism and magmatism using information from modern and ancient systems. For the sources, we review the current understanding of volcanic emissions, and explore the relative contributions and importance of magma-derived degassing versus volatile release from sediments affected by igneous intrusions and lava. In addition, we explore the various ways in which LIPs can reduce atmospheric concentrations of these same elements. The relative influences of each source and sink are in part determined by the mode of LIP emplacement and eruption style, along with the subsequent timescales of such effects. We focus on a few key examples, including the Siberian Traps, the Paraná-Etendeka, and the Central Atlantic Magmatic Province (CAMP), to demonstrate how the environmental impact can vary considerably with differing modes of emplacement, LIP duration, and eruption styles. In particular, we show that the host rocks can have a dominant role as a source or sink of emissions, depending on the lithologies affected by the LIP emplacement.