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 Liliput Effect Noted for the Devonian Mass Extinctions

When times are good, it pays to be the big fish in the sea; in the aftermath of disaster, however, smaller is better.

According to new research led by the University of Pennsylvania's Lauren Sallan, a mass extinction 359 million years ago known as the Hangenberg event triggered a drastic and lasting transformation of Earth's vertebrate community. Beforehand, large creatures were the norm, but, for at least 40 million years following the die-off, the oceans were dominated by markedly smaller fish.

"Rather than having this thriving ecosystem of large things, you may have one gigantic relict, but otherwise everything is the size of a sardine," said Sallan, an assistant professor in Penn's Department of Earth and Environmental Science in the School of Arts & Sciences.

The finding, which suggests that small, fast-reproducing fish possessed an evolutionary advantage over larger animals in the disturbed, post-extinction environment, may have implications for trends we see in modern species today, such as in fish populations, many of which are crashing due to overfishing. The research is reported in Science.

link.

Severe Selenium Depletion Detected During Ordovician, Devonian and Triassic Mass Extinctions

Severe Selenium depletion in the Phanerozoic oceans as a factor in three global mass extinction events

Authors:

Long et al

Abstract:

Selenium (Se) is one of the key trace elements required by all animal and most plant life, and Se deficiencies in the food chain cause pathologies or death. Here we show from new geochemical analyses of trace elements in Phanerozoic marine pyrite that sustained periods of severe Se depletion in the past oceans correlate closely with three major mass extinction events, at the end of the Ordovician, Devonian and Triassic periods. These represent periods of Se depletion > 1.5-2 orders of magnitude lower than current ocean abundances, being within the range to cause severe pathological damage in extant Se-reliant organisms. Se depletion may have been one of several factors in these complex extinction scenarios. Recovery from the depletion/extinction events is likely part of a natural marine cycle, although rapid rises in global oxygen from sudden major increases in marine productivity and plant biomass after each extinction event may also have played a crucial role.

Lungfish Remained Morphologically Diverse Through Romer's Gap

Lungfish diversity in Romer's Gap: reaction to the end-Devonian extinction

Authors:

Smithson et al

Abstract:

Romer's Gap, the interval following the end-Devonian extinction event, has been described as a post-extinction trough for vertebrates. It is a time roughly equivalent to the Tournaisian stage of the early Carboniferous and has been characterized by a lull in diversity of survivors. Lungfish typified this description. One species was known from one locality. Recently, a diverse collection of lungfish tooth plates, representing seven new forms, was recovered from new Tournaisian vertebrate localities in northern Britain. They display a range of previously unknown morphologies, with tooth shape and wear patterns not seen in other post-Devonian forms. A comparison of tooth ridge number and tooth ridge angle in lungfishes from the Famennian, Tournaisian and Visean reveals marked differences between late Devonian and early Carboniferous taxa. The most common tooth plate shape in the Famennian is absent from our sample of Tournaisian taxa. Two completely new shapes have evolved, one with a relatively low tooth ridge angle, no greater than 40°, in which most of the tooth ridges are essentially parallel, and the other with a much higher tooth ridge angle of up to 180° where the tooth ridges are highly divergent. This high level of morphological diversity over a narrow time period suggests that, following the end-Devonian extinction, gaps in ecospace left by the extinction of major groups of fishes were exploited by a previously unrecorded radiation of lungfishes. Whilst taxonomic diversity of lungfishes declined following the end-Devonian extinction, recovery and diversification among tooth-plated forms was rapid, and morphological disparity among these forms subsequently increased. Contrary to previous assumptions, morphological disparity among lungfish did not decline until much later in the Carboniferous.

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.

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.

Jawless Fish (Ostracoderms) Went Extinct due to Environmental Factors, Range Restriction, not Competition With Jawed Fish

Discriminating signal from noise in the fossil record of early vertebrates reveals cryptic evolutionary history

Authors:

Sansom et al

Abstract:

The fossil record of early vertebrates has been influential in elucidating the evolutionary assembly of the gnathostome bodyplan. Understanding of the timing and tempo of vertebrate innovations remains, however, mired in a literal reading of the fossil record. Early jawless vertebrates (ostracoderms) exhibit restriction to shallow-water environments. The distribution of their stratigraphic occurrences therefore reflects not only flux in diversity, but also secular variation in facies representation of the rock record. Using stratigraphic, phylogenetic and palaeoenvironmental data, we assessed the veracity of the fossil records of the jawless relatives of jawed vertebrates (Osteostraci, Galeaspida, Thelodonti, Heterostraci). Non-random models of fossil recovery potential using Palaeozoic sea-level changes were used to calculate confidence intervals of clade origins. These intervals extend the timescale for possible origins into the Upper Ordovician; these estimates ameliorate the long ghost lineages inferred for Osteostraci, Galeaspida and Heterostraci, given their known stratigraphic occurrences and stem–gnathostome phylogeny. Diversity changes through the Silurian and Devonian were found to lie within the expected limits predicted from estimates of fossil record quality indicating that it is geological, rather than biological factors, that are responsible for shifts in diversity. Environmental restriction also appears to belie ostracoderm extinction and demise rather than competition with jawed vertebrates.

Palaeoenvironmental Changes Recorded in Givetian-Frasnian Devonian Reef Systems From Australia

Changes of palaeoenvironmental conditions recorded in Late Devonian reef systems from the Canning Basin, Western Australia: A biomarker and stable isotope approach

Authors:

Tulipani et al

Abstract:

Although the Late Devonian extinctions were amongst the largest mass extinction events in the Phanerozoic, causes, nature and timing of these events remain poorly restrained. In addition to the most pronounced biodiversity loss at the Frasnian-Famennian (F-F) boundary and the end Famennian, there were also less extensively studied extinction pulses in the Middle to Late Givetian and the Frasnian. Here we used a combination of palynological, elemental, molecular and stable isotope analyses to investigate a sedimentary record of reef-systems from this time period in the Canning Basin, Western Australia.

The acquired data generally showed distinct variations between sediments from (i) the time around the Givetian-Frasnian (G-F) boundary and (ii) later in the Frasnian and indicated a distinct interval of biotic stress, particularly for reef-builders, in the older sediments. Alterations of pristane/phytane ratios, gammacerane indices, Chlorobi biomarkers, δDkerogen and chroman ratios describe the change from a restricted marine palaeoenvironment with an anoxic/euxinic hypolimnion towards a presumably open marine setting with a vertically mixed oxic to suboxic water column. Simultaneous excursions in δ13C profiles of carbonates, organic matter (OM) and hydrocarbons in the older sediments reflect the stratification-induced enhancement of OM-recycling by sulfate reducing bacteria. Alterations in sterane distributions and elevated abundances of methyltrimethyltridecylchromans (MTTCs) and perylene indicate an increased terrigenous nutrient input via riverine influx, which would have promoted stratification, phytoplankton blooms and the development of lower water column anoxia.

The detected palaeoenvironmental conditions around the G-F boundary may reflect a local or global extinction event. Our data furthermore suggest a contribution of the higher plant-expansion and photic zone euxinia to the Late Devonian extinctions, consistent with previous hypotheses. Furthermore, this work might contribute to the understanding of variations in Devonian reef margin and platform-top architecture, relevant for petroleum exploration and development in the global Devonian hydrocarbon resources.

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.

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.

A Refugium Found in Frasnian–Famennian Devonian Australia

Oxic facies and the Late Devonian mass extinction, Canning Basin, Australia

Authors:

George et al

Abstract:

The close association of anoxic or dysoxic sedimentary rocks and the major Late Devonian (Frasnian–Famennian) mass extinction has focused considerable attention on anoxia as the major cause or as a major factor in a multicausal scenario. The record of the Late Devonian biotic crisis in the well-known reef complexes of northwestern Australia (Canning Basin), in contrast to many localities elsewhere, does not display sedimentological evidence of anoxia through the Frasnian–Famennian boundary interval. Analysis of continuous drill core through this interval has yielded three positive δ13C isotopic excursions, only one of which coincides with total organic carbon (TOC) maxima in our data. Multi-element geochemical proxies suggest that TOC maxima preceding positive shifts in δ13C most likely resulted from higher productivity caused by nutrient influx from continental weathering, given the close association between TOC maxima and regional relative sea-level falls. Our interpretation supports the view that anoxia was not a fundamental driver of mass extinction and stresses the importance of integrated data sets and understanding regional controls on environmental changes and/or stresses.

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.

Ecological Implications of Mass Extinction are Separate From Taxonomic Implications

Contrasting the ecological and taxonomic consequences of extinction

Authors:

Christie et al

Abstract:

Extinction in the fossil record is most often measured by the percentage of taxa (species, genera, families, etc.) that go extinct in a certain time interval. This is a measure of taxonomic loss, but previous work has indicated that taxonomic loss may be decoupled from the ecological effects of an extinction. To understand the role extinction plays in ecological change, extinction should also be measured in terms of loss of functional diversity. This study tests whether ecological changes increase correspondingly with taxonomic changes during the Late Ordovician M4/M5 extinction, the Ordovician/Silurian mass extinction, and the Late Devonian mass extinction. All three extinctions are evaluated with regional data sets from the eastern United States. Ecological effects are measured by classifying organisms into ecological lifestyles, which are groups based on ecological function rather than evolutionary history. The taxonomic and ecological effects of each extinction are evaluated with additive diversity partitioning, detrended correspondence analysis, and relative abundance distributions. Although the largest taxonomic changes occur in the Ordovician/Silurian extinction, the largest ecological changes occur in the Late Devonian extinction. These results suggest that the ecological consequences of extinction need to be considered in addition to the taxonomic effects of extinction.

After Devonian Hangenberg Extinction, Fish Crushed Their Food

Trends in shell fragmentation as evidence of mid-Paleozoic changes in marine predation

Authors:

Salamon et al

Abstract:

Recent observations indicate that shell fragmentation can be a useful tool in assessing crushing predation in marine communities. However, criteria for recognizing shell breakage caused by durophagous predators versus physical factors are still not well established. Here, we provide data from tumbling and aquarium experiments to argue that physical and biotic processes lead to different patterns of shell damage, specifically that angular shell fragments are good indicators of durophagous predation. Using such angular shell fragments as a predation proxy, we analyze data from 57 European Paleozoic localities spanning the Ordovician through the Mississippian. Our results reveal a significant increase in angular shell fragments (either occurring as isolated valves or present in regurgitalites) in the Mississippian. The timing of this increase is coincident with the increased diversity of crushing predators as well as marked anti-predatory changes in the architecture and mode of life of invertebrate prey observed after the end-Devonian Hangenberg extinction (359 Ma). More specifically, the observed trend in shell fragmentation constitutes strong and independent confirmation of a recently suggested end-Devonian changeover in the primary method of fish predation from shearing to crushing. These results also highlight the important effect of extinction events, not only on taxonomic diversity, but also on the nature of predator-prey interactions.

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. 

More Evidence of the Devonian Shift From Hot House to Ice House Global COnditions

Sequence stratigraphic hierarchy of the Upper Devonian Foreknobs Formation, central Appalachian Basin, USA: Evidence for transitional greenhouse to icehouse conditions

Authors:

1. Wilson S. McClung (a)
2. Kenneth A. Eriksson (b)
3. Dennis O. Terry Jr. (c)
4. Clifford A. Cuffey (a)

Affiliations:

a. Chevron USA Inc, 15 Smith Rd, Midland, TX 79705

b. Department of Geosciences, Virginia Tech, Blacksburg, VA 24061

c. Department of Earth and Environmental Science, Temple University, Philadelphia, PA 19122

Abstract:

The Foreknobs Formation (Upper Devonian; Upper Frasnian to basal Famennian) comprises the uppermost marine strata of the progradational “Catskill clastic wedge” of the south-central Appalachian Mountains (Virginia-West Virginia; USA). The Foreknobs Formation consists of 14 lithofacies arranged in four facies associations which record the following depositional settings: 1) storm-dominated distal to proximal offshore to shoreface (facies association A); 2) sharp-based conglomeratic shoreface (facies association B); 3) fluvial redbed (facies association C); and 4) incised-valley fill (IVF; facies association D). Vertical juxtaposition and stacking patterns of lithofacies and facies associations permits recognition of a hierarchy of three scales of cyclicity. Up to 70 short-term 5th-order cycles, each averaging ~ 65 Kyr, consist of coarsening-upward parasequences of storm-dominated offshore marine facies in the distal setting which correspond to high frequency (unconformity bound) sequences (HFS) of fluvial redbed strata overlain by offshore marine strata in the proximal setting. These facies relationships are a consequence of 10 – 15 m of sea-level fluctuations. Up to 12 intermediate-term 4th-order cycles, each averaging ~ 375 Kyr, consist of stacked 5th-order cycles. The 4th-order cycles are bounded by regressive surfaces of marine erosion (RSME) at the base of sharp-based conglomeratic shoreface sandstones in the distal setting that correspond with paleosols in the proximal setting. In some cases, the 5th-order cycles within each 4th-order cycle exhibit stacking patterns indicative of increasing or decreasing accomodation space. These facies relationships are a consequence of 25 – 35 m of sea-level fluctuations. Three complete and portions of two additional 3rd-order cycles, each averaging ~ 1.12 Myr, consist of stacked 4th-order cycles. The 3rd-order sea-level trends reflected in the Foreknobs Formation are nearly identical to published eustatic sea-level curves. Incised-valley fills are present at one of the 3rd-order cycle boundaries and are a consequence of a 35 – 45 m sea-level fluctuation. The amplitudes of the inferred sea-level fluctuations are comparable to the expansion and contraction of ice volumes within the current Greenland and Antarctic ice sheets which suggests glacioeustasy was the primary control on sea-level fluctuations and cyclicity within the Foreknobs Formation. Such an interpretation is consistent with knowledge of Devonian climate, transitioning from Middle Devonian greenhouse to Late Devonian icehouse, as indicated by evidence of glaciation during parts of the Late Devonian in South America and the Appalachians.

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.