Ichthyostegid-like & Whatcheeriid-like Tetrapods Found in Famennian Devonian Belgium

New discoveries of tetrapods (ichthyostegid-like and whatcheeriid-like) in the Famennian (Late Devonian) localities of Strud and Becco (Belgium)

Authors:

Olive et al

Abstract:

The origin of tetrapods is one of the key events in vertebrate history. The oldest tetrapod body fossils are Late Devonian (Frasnian–Famennian) in age, most of them consisting of rare isolated bone elements. Here we describe tetrapod remains from two Famennian localities from Belgium: Strud, in the Province of Namur, and Becco, in the Province of Liège. The newly collected material consists of an isolated complete postorbital, fragments of two maxillae, and one putative partial cleithrum, all from Strud, and an almost complete maxilla from Becco. The two incomplete maxillae and cleithrum from Strud, together with the lower jaw previously recorded from this site, closely resemble the genus Ichthyostega, initially described from East Greenland. The postorbital from Strud and the maxilla from Becco do not resemble the genus Ichthyostega. They show several derived anatomical characters allowing their tentative assignment to a whatcheeriid-grade group. The new tetrapod records show that there are at least two tetrapod taxa in Belgium and almost certainly two different tetrapod taxa at Strud. This locality joins the group of Devonian tetrapod-bearing localities yielding more than one tetrapod taxon, confirming that environments favourable to early tetrapod life were often colonized by several tetrapod taxa.

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.

Revising the Frasnian–Famennian Devonian Boundary and Kellwasser Events

Revised correlation of the Frasnian–Famennian boundary and Kellwasser Events (Upper Devonian) in shallow marine paleoenvironments of New York State

Authors:

Bush et al

Abstract:

The Frasnian–Famennian boundary (Upper Devonian) is exposed in a 200 km-long outcrop belt in New York State, with deeper paleoenvironments to the west and shallower ones to the east. Geochronology in the eastern end of the outcrop belt has been based primarily on lithostratigraphic correlation with western sections, which were dated using conodonts. We collected conodonts and brachiopods from several measured sections and numerous other localities, and these collections suggest that these east–west lithostratigraphic correlations require revision. We correlate the Wiscoy Formation with the upper Angola Formation and the Canaseraga with the upper Hanover. Thus, the Canaseraga Formation contains the Frasnian–Famennian boundary and Upper Kellwasser Event, and the dark shale above the Wiscoy is equivalent to the Pipe Creek Formation and Lower Kellwasser Event. These new correlations imply that the Lower Kellwasser Event had greater impact on the shelly benthos of New York than the Upper Kellwasser, at least for the subset of taxa examined here. All strophomenid brachiopods and rugose corals were extirpated at the Lower Kellwasser, along with numerous other brachiopods. The final species of atrypid brachiopod persisted to the Upper Kellwasser.

Famennian Devonian Acanthostega gunnari Skull Reconstructed

360 million-year-old tetrapods may have been more like modern crocodiles than previously thought, according to 3D skull reconstruction. The results publish March 11, 2015 in the open-access journal PLOS ONE by Laura Porro from University of Bristol, UK, and colleagues.

Acanthostega gunnari was a 'four-footed' vertebrate, also known as a tetrapod, that invaded land during one of the great evolutionary transitions in Earth's history, 380-360 million years ago. This species is crucial for understanding the anatomy and ecology of the earliest tetrapods; however, after hundreds of millions of years buried in the ground, fossils are often damaged and deformed. To try to reconstruct the skull of this species from numerous skull pieces, the authors of the study applied high-resolution X-ray computed tomography (CT) scanning to several specimens of Acanthostega gunnari from East Greenland.

Researchers found that the reconstructed skull had a longer postorbital region and a more strongly hooked lower jaw than previously thought. They also found clues as to how the species fed. The size and distribution of its teeth and the shape of contacts between individual bones of the skull (called sutures) suggest Acanthostega may have initially seized prey at the front of its jaws using its large front teeth and hook-shaped lower jaw.

link.

Famennian Devonian to Mississippian Carboniferous Events of the Western USA

Uppermost Devonian (Famennian) to Lower Mississippian events of the western U.S.: Stratigraphy, sedimentology, chemostratigraphy, and detrital zircon geochronology

Authors:

Cole et al

Abstract:

Upper Devonian to Lower Mississippian strata in Utah and Montana record global events through this important interval in Earth history. Late Famennian strata of the Beirdneau, Leatham, and Pilot Shale formations in Utah, and Three Forks and Sappington formations in Montana, record widespread deposition of generally fine-grained siliciclastic and carbonate strata. Integration of sedimentology, physical stratigraphy, chemostratigraphy, and published biostratigraphy allows for the recognition of important disconformities and regional stratigraphic patterns. These enable the reconstruction of uppermost Devonian to lowermost Mississippian depositional, tectonic, and eustatic history of the region.

Carbon isotopic data allows for stratigraphic evaluation of the presence and absence of global bioevents of the Late Devonian, including the Annulata, Dasberg, and Hangenberg events, some of which are clearly recorded in hinterland deposits to the east in Colorado. While the Devonian–Mississippian boundary is also missing in our sections, a significant positive shift in δ13Ccarb in Lower Mississippian strata in Utah and Montana represents one of the largest positive δ13Ccarb isotope excursions of the Phanerozoic, linked to drawdown of atmospheric CO2 and glaciation in the Kinderhookian.

Detrital zircon spectra from latest Devonian to Early Mississippian strata of Utah and Colorado include populations representing derivation from the Mazatzal and Yavapai provinces, Middle Proterozoic anorogenic granite bodies, and a small influx of Grenville and presumed Appalachian–Caledonian grains. Minor Paleoproterozoic and Late Archean peaks in Utah are likely multiple generation grains originally derived from the Peace River Arch of northwestern Canada and recycled in Ordovician rocks of Nevada. These patterns in detrital zircon geochronological data reflect, in part, changes in sediment dispersal patterns due to tectonic and eustastic variability within the Antler foreland basin during the Devonian–Mississippian boundary interval. This variability also led to irregular spatial patterns of unconformity development, as well as complicated physical stratigraphic and chemostratigraphic architecture.

Anoxia was Gradual in Appalachian During Frasnian–Famennian Kellwasser Event

THE LAST GASP: TRACE FOSSILS TRACK DEOXYGENATION LEADING INTO THE FRASNIAN–FAMENNIAN EXTINCTION EVENT

Authors:

Boyer et al

Abstract:

The Frasnian–Famennian boundary is correlated with one of several Late Devonian extinction pulses that resulted in a significant decrease in diversity as well as ecological restructuring. This event is recognized within the globally correlated Upper Kellwasser interval that is well exposed and biostratigraphically well constrained in shale units of western New York State. The ichnological and geochemical signals of the interval stratigraphically below the Upper Kellwasser event at these localities provides insight into the onset of this important extinction event. Detailed analysis of ichnogeneric composition, relative size of burrow populations, amount of bioturbation, and trace metal concentrations vary in concert. Deep-penetrating, pyritized Skolithos burrows terminate abruptly at a thin, laminated black shale interval with enriched Mo levels, up to 31 ppm, and are overlain by an interval of gray-green bioturbated shales dominated by Chondrites. These textural and chemical shifts reveal that bottom-water oxygen levels decrease rapidly below the base of the Upper Kellwasser interval. Relative oxygen levels are interpreted to remain low through the Chondrites-dominated interval, with protracted stressed conditions followed by a gradual decrease to anoxic conditions within the Upper Kellwasser interval. These results suggest that, at least locally in the Appalachian Basin, bottom-water oxygen stress and/or fluctuating oxygen conditions were present leading up to the extinction event. This evidence does not support an instantaneous onset of anoxia as causal mechanism for extinction.

Academic Bun Fight! Forest Fires as Root Cause of the Famennian-Frasnian Devonian Mass Extinction

Reply to the comment on Kaiho et al., “A forest fire and soil erosion event during the Late Devonian mass extinction” [Palaeogeography, Palaeoclimatology, Palaeoecology 392 (2013): 272–280]

Authors:

Kaiho et al

Abstract:

Kaiho et al. (2013) showed that high values of organic molecule indices of combustion, soil erosion, and euxinia occurred at the Frasnian-Famennian transition at Sinsin, Belgium. Marynowski and Racki (2014) commented on the paper. Their issues mainly address (1) the low resolution of the data, (2) the reliability of the proxies, (3) weathering as a cause of the peaks of the proxies, (4) the discrepancy between rare charcoal occurrence and the high combustion proxy, and (5) the stepwise collapse of the huge global reef ecosystem ending well before the F-F boundary. In response to comment (1), the positive excursion of δ13Ccarb marking the F-F transition in the Sinsin section indicates that the Sinsin section has enough strata to detect environmental changes during the culmination of the Late Devonian stepwise mass extinction. On comment (2): soil erosion was indicated not only by dibenzofuran but also by a spike of cadalene. Dibenzothiophene should have increased when euxinic water developed on the surface of sediments, which is supported by the coincidence of isorenieratane and dibenzothiophene on the middle shelf in the late Permian. We show the combustion index at the Cretaceous-Paleogene transition, indicating that this ratio is useful as a proxy of combustion. On comment (3): we cannot explain the high and low combustion, soil erosion, and euxinia index values by weathering because of the consistently well-preserved state of the rock samples. On comment (4): we need to detect charcoal during the F-F transition and early Famennian, corresponding to maxima of high sea levels, to clarify the discrepancy. On comment (5): our model is only for the F-F transition event marked by the extinction acme; it may not explain the collapse of the reef ecosystem that ended before the F-F boundary, but it can explain the extinction acme at the F-F transition.

Three Evolutionary Radiations of Sharks During the Famennian Devonian

Paleogeographical and paleoecological constraints on paleozoic vertebrates (chondrichthyans and placoderms) in the Ardenne Massif: Shark radiations in the Famennian on both sides of the Palaeotethys

Authors:

Derycke et al

Abstract:

Three chondrichthyan radiations are registered in the Famennian of the Ardenne Massif (Belgium). These radiations are already observed in Morocco and in the Carnic Alps, their acme being related with the early expansa transgression. Comparisons of univariate statistical descriptors like Margalef richness and Shannon–Wiener diversity index show variations between both margins of the Paleotethys, variations interpreted in terms of trophic relationships. The Ardenne area, a northern shallow carbonate platform is characterized during the Famennian by endemic shark taxa with durophagous dentition. The southern open deep-sea area, the Variscan Sea, contains large placoderms probably disclosing a negative feedback on “cladodont” chondrichthyans. This supports the hypothesis that the Armorica platelet behaved like a barrier between the central southern Laurussia and northern Gondwana.

Evidence of Euxinia During the Frasnian–Famennian Devonian Mass Extinction

Geochemical evidence for euxinia during the Late Devonian extinction events in the Michigan Basin (U.S.A.)

Authors:

Formolo et al

Abstract:

Several mass extinction events occurred in the Late Devonian, but the trigger for these events remains elusive. In this study, geochemical evidence in the Late Devonian Antrim Shale, Michigan Basin, U.S.A., records episodic euxinia contemporaneous with these extinction events. Diagnostic changes in iron proxy data and elevated trace metal enrichments correspond to the Kellwasser Crisis. In this study, carbon, sulfur, iron and trace metal geochemistry preserved in the Antrim Formation validates the establishment and expansion of euxinic conditions associated with the Kellwasser Crisis and the Frasnian–Famennian boundary. The strength of the sequential extraction iron mineral data presented here, in concert with trace metal and sulfur isotope proxies, provides definitive signatures of euxinia when other data may be more ambiguous in regard to paleoredox conditions. During the time of the Frasnian–Famennian boundary extensive sulfide oxidation at the chemocline, the result of Fe-limiting conditions within the basin, provides an alternative explanation for the oceanic decline in δ34SSO4 during, and following, the Frasnian–Famennian event. Our geochemical evidence, indicating the presence of anoxia in the Michigan Basin, is consistent with data from other globally distributed locations. Euxinia should be considered a key driver for these global extinction events, and possibly others such as the Hangenberg Event in the Late Devonian.

Cosmosperma polyloba: the First Seed Plant From Famennian Devonian South China

Cosmosperma polyloba gen. et sp. nov., a seed plant from the Upper Devonian of South China

Authors:

Wang et al

Abstract:

Seed plants with ovules were abundant in the Late Devonian of Euramerica and they contribute significantly to our understanding of their early history. However, coeval ovules have been scarce in other regions of the world. Specimens of the seed plant Cosmosperma polyloba gen. et sp. nov. Wang et al. were recently obtained from the Upper Devonian (Famennian) Wutong Formation, at Fanwan Village, Changxing County, Zhejiang Province, China. This new seed plant has cupulate ovules, the uniovulate cupules with up to 16 distal segments and with minute spines on the outer surface, synangiate pollen organs bearing six to eight microsporangia fused only at the base, and planate and highly dissected pinnules in alternate arrangement. It differs from other Devonian seed plants mainly in the organization and position of the uniovulate and ornamented cupule, and in the highly dissected pinnules. Cosmosperma Wang et al. represents the first Devonian ovules recovered from China or eastern Asia and further illustrates the diversity of early spermatophytes. As for the Late Devonian seed plants, it is suggested that the pollen organs are synangiate and simple in organization, and the branches and leaves are generally planate.

Royal Tyrrell Museum Speaker Series: To Hay River and Back

Microconchid Tube Worms Dominated After Devonian Mass Extinction

Microconchid-dominated cobbles from the Upper Devonian of Russia: opportunism and dominance in a restricted environment following the Frasnian-Famennian biotic crisis

Authors:

Zatoń et al

Abstract:

Carbonate cobbles from the lower Famennian (crepida conodont Zone) brachiopod shell beds of the Russkiy Brod Quarry (Central Devonian Field, Russia) have been investigated with respect to paleoecology and paleoenvironment. The cobbles, composed of similar shell bioclasts as the host deposits, were eroded from lithified shell beds during intervals of non-deposition. The smooth surfaces and the presence of borings and encrustations on all sides suggest that the cobbles were periodically transported and overturned.

The fact that all the bioerosion traces are encrusted and none of the encrusters were bioeroded indicates that the first colonizers of the cobbles were worm-like suspension feeders, leaving long, cylindrical borings (Trypanites). The encrusting organisms are dominated by spirally-coiled microconchid tubeworms, followed by cornulitids, productid brachiopods, hederelloids, foraminifera, enigmatic Ascodictyon and trepostome bryozoans.

The high abundance but low-diversity brachiopod fauna and general rarity of such stenohaline taxa as echinoderms in the shell beds or bryozoans on the cobbles suggest that the salinity fluctuated. The presence of dolomite crystals in both the host deposit and cobbles suggests that salinity increased from normal-marine to a higher salinity level during colonization of the cobbles. In fact, as shown by the facies and palynofacies data, the cobble-bearing deposits represent near-shore, restricted environments created during the first phases of transgression of the early Famennian that followed the regional regression at the Frasnian-Famennian transition. In such shallow, restricted settings a higher salinity could have appeared seasonally during a hot and dry climate.

As with the microconchids from the aftermath of the end-Permian mass extinction, those from the post-crisis early Famennian interval of Russia were also dominant due to unstable environmental conditions. Here the periodic higher salinity episodes may have discouraged other encrusters and thus promoted the settlement of the opportunistic microconchids.

Disputing Global Conflagaration as the Cause of the Devonian Mass Extinction

Comment on the Kaiho et al., paper “A forest fire and soil erosion event during the Late Devonian mass extinction” [Palaeogeography, Palaeoclimatology, Palaeoecology 392 (2013): 272–280]

Authors:

Marynowski et al

Abstract:

Kaiho et al. (2013, Palaeogeography, Palaeoclimatology, Palaeoecology 392 (2013): 272–280) interpreted the occurrence of elevated concentrations of high molecular weight polycyclic aromatic hydrocarbons and dibenzofuran as indicators of wildfires and enhanced run-off near the Frasnian-Famennian (F-F) boundary. We argue that other processes, including weathering or hydrothermal oxidation (not discussed by Kaiho et al.) lead to the observed increase in the concentration of these compounds and also change their distribution. Kaiho et al.’s evidence for soil erosion and eutrophication-induced euxinia is also weak in the case of the investigated Belgian sections. Finally, Kaiho et al. rather unfortunately omitted a great wealth of important data published elsewhere, choosing instead to include only those which support their ideas and interpretations.

A New Model for the Kellwasser Anoxia Events of the Late Devonian

A New Model for the Kellwasser Anoxia Events (Late Devonian): Shallow Water Anoxia in an Open Oceanic Setting in the Central Asian Orogenic Belt

Authors:

Carmichael et al

Abstract:

The Frasnian-Famennian mass extinction event devastated tropical marine ecosystems and ranks in the top six in taxonomic and ecological severity. The close stratigraphic association between the extinction and the Kellwasser Anoxia Events support a link between oceanographic anoxia and extinction. The Upper and Lower Kellwasser horizons have been identified in epicontinental, basinal settings in Laurussia, Gondwana, Siberia, and South China. The Hongguleleng Formation (Late Devonian) in northwestern Xinjiang, China, contains both the Frasnian-Famennian boundary and the rebound from the Frasnian-Famennian extinction event in a highly fossiliferous shallow marine setting associated with a Devonian oceanic island arc complex (part of the Central Asian Orogenic Belt, or CAOB). Here we show that the Hongguleleng Formation also records the Upper Kellwasser Anoxia Event through analysis of multiple geochemical proxies. In contrast to previous studies asserting that the Kellwasser Events were restricted to epicontinental seaways and basins, our results indicate that it occurred not only along the shallow continental margins of the closing Rheic Ocean, but also in shallow water in the open oceanic part of Paleotethys. Previous explanations for the Kellwasser Events from epicontinental margins and basins call for the migration of deep anoxic bottom water into shallow water environments as a kill mechanism for shallow marine ecosystems or attribute it to sea level rise and subsequent stagnation. There is no evidence that the Devonian oceans completely overturned during the Kellwasser Events; similarly, many transgressive events in the Devonian are not associated with black shales. We therefore suggest an alternative mechanism for the Kellwasser Events based on new evidence from the CAOB, where anoxia is driven by episodic eutrophication of surface waters.

Coprolite Evidence of Predation From Famennian Devonian Poland

Coprolite evidence for carnivorous predation in a Late Devonian pelagic environment of southern Laurussia

Authors:

Michał ZatońCorresponding and Michał Rakociński

Abstract:

Small, light-brown and beige cylindrical structures found in the lower Famennian (Upper Devonian) shales and marls of the Holy Cross Mountains area, central Poland, have been investigated for the first time. Their compact, pellet-shaped morphology and the presence of various fossil fragments scattered within the phosphatic groundmass clearly indicate that they are coprolites. The coprolite inclusions are dominated by arthropod cuticle fragments followed by fish remains, one conodont, and one scolecodont. The arthropod cuticle fragments are represented by the crustacean-like thylacocephalan Concavicaris and three other different types of arthropods of uncertain affinity. The presence of some conical fragments resembling telsons from phyllocarid crustaceans suggests that some of the cuticle fragments may belong to that group of arthropods. The fish remains mainly consist of actinopterygian paleoniscoid scales and sarcopterygian teeth. Taking both fossil and facies characteristics into account, it is clear that the coprolites originated from a carnivorous pelagic fishes that hunted other fishes and swimming arthropods. Surprisingly, similar faunal contents consisting of paleoniscoid fishes, Concavicaris arthropods, and conodonts occur in situ within the body cavities of the Famennian cladoselachian sharks in the Cleveland Shale, Ohio. Such a coincidence suggests that at least some of the Famennian coprolites from Poland may have also been produced by pelagic carnivorous sharks. The preservation of defecated remains was influenced by an interplay between an oxygen-deficient benthic environment devoid of bioturbators and scavengers and rapid, microbially-driven phosphatization.

Frasnian–Famennian Devonian Geirud Formation in Iran has Fascinating Trace Fossils

Trace fossils analysis of fluvial to open marine transitional sediments: Example from the Upper Devonian (Geirud Formation), Central Alborz, Iran

Authors:

Sharafi et al

Abstract:

This study integrates ichnological and sedimentological data to interpret depositional environments of the mixed siliciclastic-carbonate fluvial to marine sediments of the Geirud Formation (Upper Devonian) in the central Alborz, northern Iran. Lithofacies analysis shows that these sediments are deposited in fluvial, tidal, shoreface, and shelf environments. Fluvial and tidal deposits are characterized by the presence of bi- to multi-directional cross beddings, reverse directional current ripples, low angle cross beddings, and herringbone cross beddings, with a few scattered Skolithos and Palaeophycus. Shoreface sediments, accumulated in a storm-influenced setting, are characterized by a preferentially interface and low diversity Cruziana ichnoassemblage (Rhizocorallium, Thalassinoides, Palaeophycus, Chondrites, and Ophiomorpha). In contrast to the fluvial-tidal assemblage, the storm-influenced shelf sediments display a highly diversified, mixture of dwelling and feeding forms (Arenicolites, Protovirgularia, Diplocraterion, Palaeophycus, Thalassinoides, Chondrites, and Helminthopsis), reflecting the presence of adequate food resources both in substrate and water column under normal salinity conditions. A fluvial-shelf replacement of the weakly to scarcely bioturbated sediments by the Rhizocorallium-Thalassinoides suite (Cruziana)–Chondrites-Helminthopsis (distal Cruziana) suite from the lower to upper parts of the succession clearly indicates an overall deepening upward in the Geirud Formation. In contrast to the lower part, generally of restricted environment, the upper part of the succession mainly shows open marine conditions. Ichnofabric development is controlled primarily by depositional conditions, e.g., bottom water oxygenation, sediment type, food abundance, and hydrodynamic level, which all exert control on substrate colonization style.

Evidence from Mongolian Paleontology Expedition Supports Biogenic Climate Change Causation for Late Devonian Mass Extinction

Members of a U.N.-sponsored research team with members from Appalachian State University’s Department of Geology have found evidence for catastrophic oceanographic events associated with climate change and a mass extinction 375 million years ago that devastated tropical marine ecosystems.

“The Late Devonian mass extinction was one of the five largest mass extinction events in the history of life,” said Professor Johnny Waters, who is a co-leader of the five-year, U.N. International Geoscience Programme project that began in 2011. The research team, which includes Assistant Professor Sarah Carmichael, is examining the relationship between climate change and changes in the ecosystems in the Devonian period, from 419 to 359 million years ago.

“This is the third most significant mass extinction and it was caused by plants,” Waters said. “Unlike the dinosaur mass extinction, which was related to an asteroid impact, this one was environmentally related.”

In the Devonian period, Waters explained, the world was experiencing super greenhouse climate conditions. This means that it was very warm, there probably were no ice caps, there was a lot carbon dioxide in the atmosphere (with estimates of 4,000 parts per million).

“As plant communities expanded onto land to form the first forests, they depleted the carbon dioxide (CO2) that was in the atmosphere,” Waters said. “CO2 levels dropped to 400 ppm toward the end of the Devonian. It got colder. There were glaciation events and the rapid change in the climate caused severe extinction in the tropics and the existing coral reefs became extinct.” By comparison, the world’s current CO2 level is very close to 400 ppm.

link.

Proposed Mechanism for the Frasnian-Famennian Devonian Mass Extinctions: Global Conflagration

A forest fire and soil erosion event during the Late Devonian mass extinction

Authors:

1. Kunio Kaiho (a)
2. Susumu Yatsu (a)
3. Masahiro Oba (a)
4. Paul Gorjan (b)
5. Jean-Georges Casier (c)
6. Masayuki Ikeda (d)

Affiliations:

a. Institute of Geology and Paleontology, Tohoku University, Sendai 980-8578, Japan

b. Department of Earth and Planetary Science, Washington University, St. Louis MO 63130, USA

c. Department of Paleontology, Royal Belgian Institute of Natural Sciences, rue Vautier, 29, B-1000, Brussels, Belgium

d. Faculty of Science, Ehime University, Matsuyama 790-8577, Japan

Abstract:

The Late Devonian mass extinction occurred in a stepwise manner and culminated close to the Frasnian-Famennian (F-F) boundary (372 million years ago). Organic-molecular indices from marine sedimentary rocks at the Sinsin section, Belgium, indicate that the sequence of combustion of land vegetation, soil erosion, and anoxia-euxinia occurred close to this boundary. The increased concentrations of biomarkers indicating forest fire and soil erosion measured in the Sinsin section suggest that fire became widespread at this time, leading to various damaging consequences (increased runoff and oceanic anoxia) that caused marine extinctions. Magnetic susceptibility data in the Sinsin section indicate a relatively dry climate spanning the F-F boundary, which would have encouraged forest fires. The study of organic biomarkers presents several lines of evidence to link forest fire and soil erosion to the Late Devonian mass extinction.

Comments:

 More samples from other sites.  Make sure this is not local.  Too many cases of projecting a globally what may have been a local event for paleontology.

Check for platinum group metals, please.  You know this is coming anways, get ahead of the curve.

Do some experimental tests with similar plants in the same oxygen levels.  See if you get a conflagration.  Larger size, better.  Build a big terrarium, grow some devonian analog plants (not many around, but...)  Attempt to match the paleoatmospheric content.  Pull the trigger.  Wet, dry and otherwise.  If you built this right, you can do multiple studies of multiple eras.  Past and future. 

Link Between Viluy Traps (Russia) and the Frasnian–Famennian Devonian Mass Extinction?

New 40Ar/39Ar and K-Ar ages of the Viluy traps (Eastern Siberia): Further evidence for a relationship with the Frasnian–Famennian mass extinction

Authors:

1. J. Ricci (a, b)
2. X. Quidelleur (a, b)
3. V. Pavlov (c)
4. S. Orlov (c)
5. A. Shatsillo (c)
6. V. Courtillot (d, e)

Affiliations:

a. Univ Paris-Sud, Laboratoire IDES, UMR8148, Orsay, F-91405; France

b. CNRS, Orsay, F-91405; France

c. Inst. Phys. Earth, Moscow 123995, Russia.

d. Equipe de Paléomagnétisme, Institut de Physique du Globe, UMR 7154, Sorbonne Paris Cité, F-75005, Paris, France

e. Sciences de la Terre, de l'Environnement et des Planètes, Université Paris Diderot, Sorbonne Paris Cité, F-75013, Paris, France

Abstract:

We present here new ages, combining both K-Ar and 40Ar/39Ar techniques, reinforcing the possible link between the Viluy traps (eastern Siberia) with the Late–Devonian mass extinctions. The Viluy traps (also referred to as the Yakutsk large igneous province) are associated with the breakup of the eastern margin of the Siberian platform as a triple-junction rift system, with volcanic outcropping along the Lena, Markha and Viluy rivers and an initial volume of volcanic products of about one million cubic kilometers. K-Ar ages obtained on seven samples from the Viluy rift display values ranging from 366 ± 5 to 381 ± 5 Ma, with a mean age of 374 ± 5 Ma. Our new 40Ar/39Ar results display well-defined step-heating plateau ages ranging from 362.3 ± 3.4 to 379.7 ± 3.5 Ma. Although most K-Ar and 40Ar/39Ar ages agree within about 1% uncertainty, which reinforces the validity of the K-Ar ages obtained with the Cassignol and Gillot unspiked technique (even in the Paleozoic), a slightly clearer scenario appears when only the 40Ar/39Ar ages are considered. Effectively, they cluster in two different groups with weighted mean ages of 364.4 ± 1.7 and 376.7 ± 1.7 Ma. These ages support a multi-phases emplacement of the Viluy traps, as is the case for many continental flood basalts. Because the age of the first volcanic phase is undistinguishable from recent determinations of the age of the Frasnian–Famennian boundary, our results further strengthen the hypothesis of a causal relationship between the two events. The second phase of emplacement of the Viluy traps occurred at the end of the Devonian, apparently slightly before the Devonian–Carboniferous boundary. Finally, except for the Ordovician–Silurian extinction which remains to be associated with a volcanic province, all major Phanerozoic mass extinctions have been correlated with the emplacement of a CFB, thereby reinforcing the possible causal link between these events.

Timing is not everything, folks.  Extinction pattern studies are needed, too.

That said, if this holds up, supercontinents are BAD NEWS for life. 

Problems for Devonian Geochronology?

Latest Devonian (Famennian) Global Events in Western Laurentia: Variations in the Carbon Isotopic Record Linked to Diagenetic Alteration Below Regionally Extensive Unconformities

Authors:

1. Paul M. Myrow (a)
2. Anne Hanson (a)
3. Anna S. Phelps (a)
4. Jessica R. Creveling (b)
5. Justin V. Strauss (b)
6. David A. Fike (c)
7. Robert L. Ripperan (d)

Affiliations:

a. Department of Geology, Colorado College, Colorado Springs, CO 80903, USA

b. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA

c. Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA

d. 1417 Fairbrook Drive, Des Peres, MO 63131, USA

Abstract:

Integrated analysis of the sedimentology, stratigraphy, and chemostratigraphy of the uppermost Devonian Chaffee Group of Colorado reveals the presence of two regionally extensive unconformity surfaces associated with globally recognized extinction/eustatic events. The contact between semi-restricted, marginal marine, mixed siliciclastic–carbonate deposits of the Parting Formation and open marine carbonate of the Dyer Formation is a major marine flooding surface across western Colorado. This flooding surface rests at the top of a ~ 5 m thick, transgressive, cross-bedded, shoreline sandstone unit that locally overlies a 2.5-m-thick paleokarst breccia. δ13C values shift lighter across the formation contact, in some cases by as much as 5‰. Oxygen isotopic values are extremely variable between measured stratigraphic sections, in cases invariant across the contact, and in other cases covarying with the δ13C values. At Ouray, CO, δ18O covaries with δ13C throughout the section, and reaches extreme values (less than −30‰) below the unconformity. An isotopic shift in rocks of this age in Utah, coined ALFIE, was previously correlated to the Parting–Dyer contact. This study demonstrates that the carbon and oxygen isotopic record of ALFIE is highly variable across western Laurentia, and that important carbonate chemostratigraphic variations result from diagenesis that is clearly linked to a regional unconformity and associated relative sea-level fall. This lowstand may be a signal of eustatic fall associated with the Dasberg Event, a late Famennian marine extinction event. Similar isotopic patterns exist for strata below and above a paleokarst breccia in the upper Dyer Formation that we link to the globally significant latest Famennian Hangenberg Event, which includes a eustatic lowstand and subsequent transgression. Similar to the Parting–Dyer contact, both carbon and oxygen isotopes in strata below this regional unconformity surface show the variable nature of diagenetic alteration of carbonate units during lowstand conditions. Our data also suggest that correlatable δ13C chemostratigraphic shifts can be diagenetically produced during lowstands across a regionally widespread (western U.S.) basin, and that these δ13C shifts may be expressed within outcrops that show no macroscopic sedimentological signature of subaerial exposure. This has broad implications for the evaluation of δ13C data in the rock record, particularly the assumption that extensive correlatable isotopic anomalies reflect global marine signatures.