The role of giant comets in mass extinctions

2014 ◽  
Author(s):  
W.M. Napier
Keyword(s):  
Mass Extinctions ◽  
Giant Comets

THE ROLE OF GEOCHRONOLOGY IN LINKING FLOOD BASALTS TO MASS EXTINCTIONS

2018 ◽  
Author(s):  
Paul R. Renne ◽  
◽  
Benjamin A. Black ◽  
Benjamin A. Black ◽  
Isabel Fendley ◽  
...  
Keyword(s):  
Mass Extinctions ◽  
Flood Basalts

Crocodilian diversity in space and time: the role of climate in paleoecology and its implication for understanding K/T extinctions

Paleobiology ◽  
1998 ◽  
Vol 24 (4) ◽  
pp. 470-497 ◽  
Author(s):  
Paul J. Markwick
Keyword(s):  
Northern Hemisphere ◽  
Middle Eocene ◽  
Temporal Trends ◽  
Late Eocene ◽  
High Rate ◽  
Mass Extinctions ◽  
Crown Group ◽  
Climatic Effects ◽  
General Decline

The taxonomic diversity of crocodilians (Crocodylia) through the last 100 million years shows a general decline in the number of genera and species to the present day. But this masks a more complex pattern. This is investigated here using a comprehensive database of fossil crocodilians that provides the opportunity to examine spatial and temporal trends, the influence of sampling, and the role of climate in regulating biodiversity.Crown-group crocodilians, comprising the extant families Alligatoridae, Crocodylidae, and Gavialidae, show the following trend: an initial exponential diversification through the Late Cretaceous and Paleocene that is restricted to the Northern Hemisphere until after the K/T boundary; relatively constant diversity from the Paleocene into the middle Eocene that may be an artifact of sampling, which might mask an actual decline in numbers; low diversity during the late Eocene and Oligocene; a second exponential diversification during the Miocene and leveling off in the late Miocene and Pliocene; and a precipitous drop in the Pleistocene and Recent. The coincidence of drops in diversity with global cooling is suggestive of a causal link—during the initial glaciation of Antarctica in the Eocene and Oligocene and the Northern Hemisphere glaciation at the end of the Pliocene. However, matters are complicated in the Northern Hemisphere by the climatic effects of regional uplift.Although the global trend of diversification is unperturbed at the K/T boundary, this is largely due to the exceptionally high rate of origination in the early Paleocene. Nonetheless, the survival of such a demonstrably climate-sensitive group strongly suggests that a climatic explanation for the K/T mass extinctions, especially the demise of the dinosaurs, must be reconsidered.

scholarly journals Evolutionary catastrophes and the Goldilocks problem

2007 ◽  
Vol 6 (4) ◽  
pp. 325-329 ◽  
Author(s):  
Milan M. Ćirković
Keyword(s):  
Rare Earth ◽  
Milky Way ◽  
Human Life ◽  
Biological Evolution ◽  
Selection Effects ◽  
Mass Extinctions ◽  
Terrestrial Biosphere ◽  
Habitable Planet ◽  
Observation Selection

AbstractOne of the mainstays of the controversial ‘rare Earth’ hypothesis is the ‘Goldilocks problem’ regarding various parameters describing a habitable planet, partially involving the role of mass extinctions and other catastrophic processes in biological evolution. Usually, this is construed as support for the uniqueness of the Earth's biosphere and intelligent human life. Here it is argued that this is a misconstrual and that, on the contrary, observation-selection effects when applied to catastrophic processes make it very difficult for us to discern whether the terrestrial biosphere and evolutionary processes which created it are exceptional in the Milky Way or not. This agnosticism, in turn, supports the validity and significance of practical astrobiological and SETI research.

scholarly journals The important role of private wildlife organisations in facilitating scientific research: A case study of the Australian Dingo Foundation

2020 ◽  
Author(s):  
Bradley P. Smith ◽  
Shennai G. Palermo ◽  
Lyn Watson
Keyword(s):  
Captive Breeding ◽  
Scientific Literature ◽  
Mass Extinctions ◽  
The Past ◽  
Lethal Management ◽  
Conducting Research ◽  
Free Ranging ◽  
Private Organisation

As we enter an era of global mass extinctions, it is important to tackle wildlife research and conservation from multiple fronts, including those made available by wildlife organisations, zoos and sanctuaries. Captive studies are particularly useful when studying free-ranging populations is difficult, and/or when controlled conditions are required. Yet, despite the significant role that they play in supporting research and conservation of species and ecosystems, they are rarely recognised in the scientific literature. Here we present a case study of the Australian Dingo Foundation (ADF), a private organisation and captive breeding facility that actively supports research and conservation efforts relating to the dingo ( Canis dingo). Over the past decade (2010 to 2020), the ADF has facilitated research across eight research disciplines that include archaeology, behaviour, biology, cognition, evolutionary psychology, non-lethal management, reproduction and parental behaviour, and vocalisations. This has resulted in at least 21 published scientific studies which are summarised in this paper. As this case study demonstrates, captive facilities have the potential to contribute to the understanding and conservation of dingoes by providing practical alternatives to, and/or supplement studies of free-ranging populations. We conclude by outlining some of the implications and limitations of conducting research using captive dingo populations.

Calcite interval in aragonite seas: Geochemical characterization of post-extinction oolites at the Triassic-Jurassic boundary and their implications

2021 ◽  
Author(s):  
Ingrid Urban ◽  
Sylvain Richoz
Keyword(s):  
Mass Extinction ◽  
Major And Trace Elements ◽  
Late Triassic ◽  
Geochemical Data ◽  
Mass Extinctions ◽  
Icp Ms ◽  
Petrographic Analyses ◽  
Isotope System ◽  
Extinction Events

<p>The End-Triassic Mass Extinction (ETME) is one of the five major mass extinctions of the Phanerozoic. The deposition of ooids is atypically high in the direct aftermath of major extinction events, including the ETME. Ooids were intensively investigated both petrographically and sedimentologically in the past decades; but only recently their potentialities as archives for the original chemical composition of the oceans where they formed, have gained awareness. Here we present stratigraphical, sedimentological and geochemical aspects for a mid-Norian-Hettangian section from the Emirates.</p><p>Petrographic analyses provided a detailed morphological classification of post-ETME coated grains, supported by point counting of two isochronous geological sections. FE-SE-EDX imaging unraveled peculiar µm-scale features linked to morphology, diagenesis and biotic interaction in the cortex. LA-ICP-MS analyses were performed for specific major and trace elements. Post-extinction oolites show high variability in size and development of the cortex. They range from small (~ 300 µm) and superficial coating, to bigger (up to 800 µm) and well developed. The degree of micritization highlights different oxic conditions in the diagenetic environment. LA-ICP-MS analyses give insights into seawater redox conditions during ooids formation, siliciclastic contamination, diagenetic processes and the role of bacterial strain in shaping the ooids. Petrographical and geochemical data point out to a calcitic deposition of these ooids as odd with the general consideration that the Late Triassic to Early Jurassic was part of the Aragonite sea. This has major implication on the understanding of the carbonate saturation in the oceans just after the mass-extinction and on the interpretation of several proxies as the C and Ca isotope-system.</p><p> </p><p> </p>

scholarly journals Giant comets and mass extinctions of life

2015 ◽  
Vol 448 (1) ◽  
pp. 27-36 ◽  
Author(s):  
W. M. Napier
Keyword(s):  
Mass Extinctions ◽  
Giant Comets
Sign in / Sign up

Export Citation Format

Share Document