late Frasnian mass extinction

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Aftermath of the late Frasnian mass extinction (Upper Devonian) on brachiopods in the Namur-Dinant Basin (Belgium).

Aftermath of the late Frasnian mass extinction (Upper Devonian) on brachiopods in the Namur-Dinant Basin (Belgium).

Due to their diversity and their abundance in Frasnian communities, brachiopods are prime tools for evaluating the extinction events related to the late Frasnian mass extinction whose causes are still hotly disputed. In the Namur-Dinant Basin (southeastern margin of Laurussia), Frasnian brachiopod decline occurred in three steps within the interval spanning the Lower rhenana conodont Zone to the linguiformis Zone. The major losses occurred at the top of the Upper rhenana Zone. These extinction episodes were linked principally to diachronous regional facies changes related to transgressions. Atrypids and pentamerids disappeared at the top of the Lower rhenana Zone in the deeper part of the basin, just before the deposition of the dark shales (indicative of hypoxic bottom conditions) of the Matagne Formation, but persisted within the Upper rhenana Zone in its shallow parts. The linguiformis Zone yielded only productids (Chonetidina), rhynchonellids and lingulids. Post-extinction brachiopod recovery was rapid in the basal Famennian but, despite their great abundance, their diversity was quite low. At present, only one surviving athyridid species (Lazarus taxon) is definitely recognized in the lower Famennian. New cosmopolitan spiriferid, athyridid and rhynchonellid genera appeared at this time concomitantly with new species of pre-existing orthid and
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Aftermath of the late Frasnian mass extinction on brachiopods and corals in the Namur-Dinant Basin (southern Belgium)

Aftermath of the late Frasnian mass extinction on brachiopods and corals in the Namur-Dinant Basin (southern Belgium)

ORAL Due to their diversity and their abundance in the Frasnian communities, brachiopods and corals are prime tools for highlighting the extinction events related to the late Frasnian mass extinction whose causes are still disputed [1]. Both phyla have been studied in detail within the Namur-Dinant Basin (Namur and Dinant synclinoria, Vesdre area) which corresponds to the historical type area of the Frasnian and

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Precisely dating the Frasnian–Famennian boundary: implications for the cause of the Late Devonian mass extinction

Precisely dating the Frasnian–Famennian boundary: implications for the cause of the Late Devonian mass extinction

L. M. E. Percival 1 , J. H. F. L. Davies 2 , U. Schaltegger 2 , D. De Vleeschouwer 3 , A.-C. Da Silva 4,5 & K. B. Föllmi 1 The Frasnian–Famennian boundary records one of the most catastrophic mass extinctions of the Phanerozoic Eon. Several possible causes for this extinction have been suggested, including extra- terrestrial impacts and large-scale volcanism. However, linking the extinction with these potential causes is hindered by the lack of precise dating of either the extinction or volcanic/impact events. In this study, a bentonite layer in uppermost-Frasnian sediments from Steinbruch Schmidt (Germany) is re-analysed using CA-ID-TIMS U-Pb zircon geochronology in order to constrain the date of the Frasnian–Famennian extinction. A new age of 372.36 ± 0.053 Ma is determined for this bentonite, confirming a date no older than 372.4 Ma for the Frasnian–Famennian boundary, which can be further constrained to 371.93–371.78 Ma using a pre-existing Late Devonian age model. This age is consistent with previous dates, but is significantly more precise. When compared with published ages of the Siljan impact crater and basalts produced by large-scale volcanism, there is no apparent correlation between the extinction and either phenomenon, not clearly supporting them as a direct cause for the Frasnian– Famennian event. This result highlights an urgent need for further Late Devonian geochronological and chemostratigraphic work to better understand the cause(s) of this extinction.
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Timing and Pacing of the Late Devonian Mass extinction event regulated by eccentricity and obliquity

Timing and Pacing of the Late Devonian Mass extinction event regulated by eccentricity and obliquity

The Late Devonian envelops one of Earth’s big five mass extinction events at the Frasnian–Famennian boundary (374 Ma). Environmental change across the extinction severely affected Devonian reef-builders, besides many other forms of marine life. Yet, cause- and-effect chains leading to the extinction remain poorly constrained as Late Devonian stratigraphy is poorly resolved, compared to younger cataclysmic intervals. In this study we present a global orbitally calibrated chronology across this momentous interval, applying cyclostratigraphic techniques. Our timescale stipulates that 600 kyr separate the lower and upper Kellwasser positive δ 13 C excursions. The latter excursion is paced by obliquity and is therein similar to Mesozoic intervals of environmental upheaval, like the Cretaceous Ocean-Anoxic-Event-2 (OAE-2). This obliquity signature implies coincidence with a minimum of the 2.4 Myr eccentricity cycle, during which obliquity prevails over precession,
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Unusual biological association event within the Late Frasnian Crisis

Unusual biological association event within the Late Frasnian Crisis

More than sudden mass extinction, the Late Frasnian Crisis has led to the weakening of ecosystems in a damaged environment. The upper member of the Aisemont Formation is such an environment where opportunistic organisms have constituted a remarkable association of common Devonian fauna in an unusual facies.

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Bilateral Alternating Auditory Stimulations Facilitate Fear Extinction and Retrieval

Bilateral Alternating Auditory Stimulations Facilitate Fear Extinction and Retrieval

Publiques des Hôpitaux de Marseille, Service Central de Biophysique et Médecine Nucléaire, Marseille, France, 6 Centro de Estudios de Argumentación y Razonamiento, Facultad de Psicología, Universidad Diego Portales, Santiago, Chile Disruption of fear conditioning, its extinction and its retrieval are at the core of posttraumatic stress disorder (PTSD). Such deficits, especially fear extinction delay, disappear after alternating bilateral stimulations (BLS) during eye movement desensitization and reprocessing (EMDR) therapy. An animal model of fear recovery, based on auditory cued fear conditioning and extinction learning, recently showed that BLS facilitate fear extinction and fear extinction retrieval. Our goal was to determine if these previous results found in animals can be reproduced in humans. Twenty-two healthy participants took part in a classical fear conditioning, extinction, and extinction recall paradigm. Behavioral responses (fear expectations) as well as psychophysiological measures (skin conductance responses, SCRs) were recorded. The results showed a significant fear expectation decrease during fear extinction with BLS. Additionally, SCR for fear extinction retrieval were significantly lower with BLS. Our results demonstrate the importance of BLS to reduce negative emotions, and provide a successful model to further explore the neural mechanisms underlying the sole BLS effect in the EMDR.
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Evaluation Of Frasnian Shale Reservoir, Case Study Well Dak-1, Ahnet Basin, Southern Algeria

Evaluation Of Frasnian Shale Reservoir, Case Study Well Dak-1, Ahnet Basin, Southern Algeria

3. RESULTS AND DISCUSSION 3.1 The Thermal Maurity of organic matter, The maturity was determined using gas Ratio method; in this present study the gas data recorded while drilling Frasnian shale formation show that the wetness ranging from 3.04% to 12.06%, the balance is higher than wetnees in all intervals even the character from top to the bottom of frasnian shale is lower than 0.5 (Fig.4), according to the Gas ratio flow chart of Baker Hughes the frasnian shale formation product wet gas, which indicate that the trapped organic matter in Frasnian shale is mature.
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Adaptation in a heterogeneous environment. I: Persistence versus extinction

Adaptation in a heterogeneous environment. I: Persistence versus extinction

On the biological interpretation of the main results. For problem (1) with fitnesses (3), Proposition 2.7 together with Theorems 2.4-2.5 show that the more the two environments are connected by migration (i.e., when δ is increased), the lower are the chances of persistence. In the absence of migration, when the two habitats are not connected (δ = 0), it was already known that persistence occurs if r max > µ n/2 [21, 26], whereas r max < µ n/2 leads to extinction (for both types of growth functions). In the case δ = 0, at large times, the mean fitness r(t) converges to r max − µ n/2, with µ n/2 the mutation load. As already mentioned, if the mutation load exceeds
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Amygdala Reward Neurons Form and Store Fear Extinction Memory

Amygdala Reward Neurons Form and Store Fear Extinction Memory

The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Zhang, Xiangyu, Joshua Kim & Susumu Tonegawa. “Amygdala Reward Neurons Form and Store Fear Extinction Memory.” Neuron 105 (2020): 1077-1093.e7

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Late Again with Defiers

Late Again with Defiers

The aim of this note is to show that actually, the Wald statistic still identifies a local average treatment effect (LATE) under a weaker condition than instrument monotonicity. As shown by Vytlacil (2002), monotonicity is equivalent to assuming a single index model for selection into treatment. In this threshold model, the unobserved term does not depend on the instrument. This means that the "taste" for treatment of an individual should be the same whether he receives the instrument or not. This is equivalent to a rank invariance assumption: the rank of an individual in the distribution of taste for treatment should not change with the instrument. What we show is that we can actually make the taste for treatment depend on the instrument, which implies that there may be some defiers. However, the unobserved terms with or without the instrument should have the same marginal distribution, conditional on potential outcomes. In other words, we show that we can replace the rank invariance condition embedded in Vytlacil’s model by a rank similarity condition (see Chernozhukov & Hansen, 2005).
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Imaging birefringent minerals without extinction using circularly polarized light

Imaging birefringent minerals without extinction using circularly polarized light

c ircularly P olarizeD l iGht Conventional petrographic microscopes use two linear polarizers to produce images of anisotropic minerals. This is generally termed cross-polarized light (XP). Unpolarized light passes through a linear polarizer, which only allows a single direction of polar- ization. This polarized light then passes through the sample, generally a thin section, where it is split into two orthogonal components. Where these components emerge from the crystal, there is a difference in phase called the retardation. The components are combined in a second, orthogonal polarizer, where interference colors are produced. The colors are controlled by the birefringence of the mineral in the direction of propaga- tion of the light. However, the intensity of the interfer- ence color will depend on the orientation of the light components with respect to the polarizers: if they are parallel, then no light will pass through, and the mineral is said to be at extinction. Hence, the intensity of the retardation color will change as the stage is rotated.
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External auditory exostoses among western Eurasian late Middle and Late Pleistocene humans

External auditory exostoses among western Eurasian late Middle and Late Pleistocene humans

Pleistocene archaic humans ( � 20%) and early modern humans (Middle Paleolithic: � 25%; Early/Mid Upper Paleolithic: 20.8%; Late Upper Paleolithic: 9.5%). The Neandertals, how- ever, exhibit an exceptionally high level of EAE (56.5%; 47.8% if two anomalous cases are considered normal). The levels of EAE for the early modern humans are well within recent human ranges of variation, frequencies which are low for equatorial inland and high latitude samples but occasionally higher elsewhere. The Early/Mid Upper Paleolithic frequency is nonetheless high for a high latitude sample under interpleniglacial conditions. Given the strong etiological and environmental associations of EAE development with exposure to cold water and/or damp wind chill, the high frequency of EAE among the Neandertals implies frequent aquatic resource exploitation, more frequent than the archeological and stable isotopic evidence for Middle Paleolithic/Neandertal littoral and freshwater resource foraging implies. As such, the Neandertal data parallel a similar pattern evident in eastern Eurasian archaic humans. Yet, factors in addition to cold water/wind exposure may well have contributed to their high EAE frequencies.
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Plicathyridine brachiopods from the Frasnian (Upper Devonian) of the Middle East and Belgium

Plicathyridine brachiopods from the Frasnian (Upper Devonian) of the Middle East and Belgium

inorganic carbon (DIC) in the water column where these specimens lived, and that the fluctuation in δ 13 C of DIC is annual, we can estimate the growth rate of Quenstedtoceras as three quarters to one whorl a year. S7 - PLICATHYRIDINE BRACHIOPODS FROM THE FRASNIAN (UPPER DEVONIAN) OF THE MIDDLE EAST AND BELGIUM

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Selective extinction against redundant species buffers functional diversity

Selective extinction against redundant species buffers functional diversity

(c) Functional diversity analyses We selected five traits (i.e. body size, life habit, locomotion, environment, and diet; electronic supplementary material, table S1) that characterize the ecological roles of Caribbean molluscs [63–65]. Traits were assigned to species using authoritative taxon-specific texts, online databases, and expert assessments based on both extant relatives and the fossil record (electronic supplementary material, dataset). There were limited differences in the number of species occurrences per trait category (electronic supplementary material, figure S6). Based on the trait assign- ments, we calculated a series of functional indices in order to evaluate changes in functional composition and structure across the Neogene and Quaternary (23.03–0.01 Ma). To make this comparison, we used the longevity of each species estimated in PyRate (i.e. the time of origination and extinction of each species; see above) to record the presence and absence of species in 23 time bins of 1 Myr each (from 23–0 Ma). Accordingly, all functional diversity analyses described below were made per time bin. Given that the age of each species at a given time bin was assigned based on their longevity, no sampling differences between time bins were detected. Nevertheless, in order to incor- porate age uncertainties, we resampled the estimated longevity of each species 100 times and performed 100 iterations of all functional diversity calculations. For each time bin, we evalu- ated: (i) the functional composition of Caribbean molluscs based on FEs or unique trait combinations (which reflects the diversity of ecological roles) and (ii) their functional structure
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"Mass Without Mass" and Nuclear Matter

"Mass Without Mass" and Nuclear Matter

It is also connected, for the number of flavors N F > 8, ∼ to the issue of dilatonic Higgs model with a view to- ward the Beyond Standard Model. Our attitude is that whether the IR fixed point is present or not in QCD proper, its notion can be implemented in nuclear pro- cesses at high density when combined with chiral symme- try, in the guise of scale-chiral perturbation theory. We find the scale symmetry, hidden or even absent in the vac- uum, can “emerge” as density increases at a dilaton-limit fixed point (DLFP) where the scalar s becomes degener- ate with the zero-mass pion in the chiral limit. This is in fact a notion associated with the dilaton condensate that has been around for a long time since the work I did
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Colour polymorphism is associated with lower extinction risk in birds

Colour polymorphism is associated with lower extinction risk in birds

extinction drivers that differ between polymorphic and non-polymorphic species. Though we were not able to detect such differences with the indices currently provided by the IUCN, the development of new global quantitative indices should help making progress in that direction. Improving current knowledge of the ecological and evolutionary mechanisms responsible for the maintenance of colour polymorphism are also fundamental steps towards a mechanistic understanding of polymorphism’s role in species responses to environmental changes. The up-to-date database provided in this study should motivate further research on these mechanisms, and on the evolution of polymorphism in general. With this study and the associated database, we hope to elicit further investigations of colour polymorphic species in the research effort to understand how phenotypic variability at the population level can influence population persistence through time and adaptation to changing environments.
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Constraints on the broad-line region properties and extinction in local Seyferts

Constraints on the broad-line region properties and extinction in local Seyferts

transition probabilities (Osterbrock & Ferland 2006 ). The H α and [N II ] 6583 Å fluxes were free parameters in the fit. We tied H γ , H β and Pa β fluxes to the Hα flux together adopting fixed intrinsic line ratios and fitting for the extinction. The extinction is likely to be different to that towards the BLR because the narrow lines originates in a physically distinct and larger region. We estimate it from Balmer and Paschen hydrogen line ratios: H α/H β, H γ /H β and H α/Pa β, adopting case B recombination line ratios assuming a temperature of 10 000 K and an electron density of 100 cm −3 , except for the H α/H β ratio which we assumed is equal 3.1 due to collisional enhancement in the NLR. We adopt a ‘screen’ dust configuration and the Wild et al. ( 2011 ) extinction law, which has the form:
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Exploring Late Pleistocene climate variations

Exploring Late Pleistocene climate variations

The stratigraphically best-resolved records for the last climate cycle have been derived from two cores drilled at the summit of Greenland.The Greenland Ice Sheet Project 2 (GISP2) a[r]

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Putative Late Ordovician land plants

Putative Late Ordovician land plants

Current available data show a rather conflicting and incomplete picture of early plant terrestrialization (Kenrick et al., 2012), leaving many key questions unanswered. A major discrepancy in time of appearance of spores and plant macrofossils is particularly intriguing. Importantly, a major change in spore types in the Late Ordovician–early Silurian, leading to the decrease of cryptospores and increase in diversity of trilete spores, was attributed to the initial radiation of vascular or pre-vascular plants (Steemans et al., 2009). However, it has to be noted that, although the fossilization potential and the evolutionary value of palynomorphs are clearly
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Finite time extinction by nonlinear damping for the Schrodinger equation

Finite time extinction by nonlinear damping for the Schrodinger equation

As a corollary to our approach, we can prove the same phenomenon for the “usual” nonlinear Schr¨odinger equation perturbed by the damping term that we consider in this paper, provided th[r]

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