The significance of multiple causes and coincidence in the geological record: from clam clusters to Cretaceous catastrophe

2001 ◽  
Vol 38 (2) ◽  
pp. 271-292 ◽  
Author(s):  
Cameron J Tsujita
Keyword(s):  
Time Scales ◽  
Mass Extinction ◽  
Flood Basalt ◽  
Global Scale ◽  
Causal Mechanism ◽  
Great Expectations ◽  
Geological Record ◽  
Wide Range ◽  
Planktotrophic Larvae ◽  
Mass Extinction Event

Specific causes of unusual events recorded in the geological record are commonly difficult to distinguish and isolate; in some instances, event strata contain features that cannot be explained by a single causal mechanism. Unicausal hypotheses, when applied to complex problems, can lead to the misidentification, misinterpretation, and force-fitting of observations ("great expectations syndrome"). The close timing or temporal overlap of significant events, although statistically improbable on short time scales, becomes possible on long time scales. Event coincidence may occur on a wide range of scales, from local to global. On the local scale, a multiple-event interpretation is offered for both the concentration and clustering of bivalves at specific levels within the Upper Cretaceous Bearpaw Formation of southern Alberta. For this example, the relative timing of fluctuations in benthic substrate texture, oxygen concentration, abundance of planktotrophic larvae, and degree of sea-floor scouring was crucial to the formation and preservation of shell concentrations. On the sharply contrasted global scale, the implications of multiple events warrant much closer consideration than they have received hitherto in terms of major proposed causes for the Cretaceous–Tertiary (K–T) mass-extinction event: bolide impact, sea-level change, climatic change, and flood-basalt volcanism. By considering the predictable effects of these synchronous factors, both individually and in combination, a multiple-cause explanation of the K–T mass extinction emerges as entirely plausible. Certainly it needs to be considered in all future investigations of this important issue.

THE RECORD OF ENVIRONMENTAL CHANGE IN NORTHEASTERN PANTHALASSA DIRECTLY PRECEDING THE END-TRIASSIC MASS EXTINCTION EVENT

2019 ◽  
Author(s):  
Ekaterina Larina ◽  
◽  
David J. Bottjer ◽  
Frank A. Corsetti ◽  
William M. Berelson ◽  
...  
Keyword(s):  
Environmental Change ◽  
Mass Extinction ◽  
Extinction Event ◽  
Mass Extinction Event

SEDIMENTARY MERCURY CONCENTRATIONS AND ISOTOPES ACROSS THE END-CRETACEOUS MASS EXTINCTION EVENT FROM NEW JERSEY

2020 ◽  
Author(s):  
Marisa D. Knight ◽  
◽  
Runsheng Yin ◽  
Clara L. Meier ◽  
James V. Browning ◽  
...  
Keyword(s):  
New Jersey ◽  
Mass Extinction ◽  
Extinction Event ◽  
Mass Extinction Event

scholarly journals Current extinction rate in European freshwater gastropods greatly exceeds that of the late Cretaceous mass extinction

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Thomas A. Neubauer ◽  
Torsten Hauffe ◽  
Daniele Silvestro ◽  
Jens Schauer ◽  
Dietrich Kadolsky ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Recovery Period ◽  
Freshwater Ecosystems ◽  
Extinction Rate ◽  
Freshwater Gastropods ◽  
Extinction Rates ◽  
Freshwater Biota ◽  
Order Of Magnitude ◽  
To Come ◽  
Mass Extinction Event

AbstractThe Cretaceous–Paleogene mass extinction event 66 million years ago eradicated three quarters of marine and terrestrial species globally. However, previous studies based on vertebrates suggest that freshwater biota were much less affected. Here we assemble a time series of European freshwater gastropod species occurrences and inferred extinction rates covering the past 200 million years. We find that extinction rates increased by more than one order of magnitude during the Cretaceous–Paleogene mass extinction, which resulted in the extinction of 92.5% of all species. The extinction phase lasted 5.4 million years and was followed by a recovery period of 6.9 million years. However, present extinction rates in European freshwater gastropods are three orders of magnitude higher than even these revised estimates for the Cretaceous–Paleogene mass extinction. Our results indicate that, unless substantial conservation effort is directed to freshwater ecosystems, the present extinction crisis will have a severe impact to freshwater biota for millions of years to come.

scholarly journals Dinosaurs in decline tens of millions of years before their final extinction

2016 ◽  
Vol 113 (18) ◽  
pp. 5036-5040 ◽  
Author(s):  
Manabu Sakamoto ◽  
Michael J. Benton ◽  
Chris Venditti
Keyword(s):  
Mass Extinction ◽  
Marked Reduction ◽  
Evolutionary Dynamics ◽  
General Pattern ◽  
Extinction Rate ◽  
Catastrophic Event ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
First Time

Whether dinosaurs were in a long-term decline or whether they were reigning strong right up to their final disappearance at the Cretaceous–Paleogene (K-Pg) mass extinction event 66 Mya has been debated for decades with no clear resolution. The dispute has continued unresolved because of a lack of statistical rigor and appropriate evolutionary framework. Here, for the first time to our knowledge, we apply a Bayesian phylogenetic approach to model the evolutionary dynamics of speciation and extinction through time in Mesozoic dinosaurs, properly taking account of previously ignored statistical violations. We find overwhelming support for a long-term decline across all dinosaurs and within all three dinosaurian subclades (Ornithischia, Sauropodomorpha, and Theropoda), where speciation rate slowed down through time and was ultimately exceeded by extinction rate tens of millions of years before the K-Pg boundary. The only exceptions to this general pattern are the morphologically specialized herbivores, the Hadrosauriformes and Ceratopsidae, which show rapid species proliferations throughout the Late Cretaceous instead. Our results highlight that, despite some heterogeneity in speciation dynamics, dinosaurs showed a marked reduction in their ability to replace extinct species with new ones, making them vulnerable to extinction and unable to respond quickly to and recover from the final catastrophic event.

scholarly journals Decoupled taxonomic and ecological recoveries from the Permo-Triassic extinction

2018 ◽  
Vol 4 (10) ◽  
pp. eaat5091 ◽  
Author(s):  
Haijun Song ◽  
Paul B. Wignall ◽  
Alexander M. Dunhill
Keyword(s):  
Time Scales ◽  
Carrying Capacity ◽  
Mass Extinction ◽  
Marine Species ◽  
Taxonomic Diversity ◽  
Marine Ecosystems ◽  
Trophic Levels ◽  
Ecosystem Structure ◽  
Top Down ◽  
Structure Building

The Permian-Triassic mass extinction was the worst crisis faced by life; it killed >90% of marine species in less than 0.1 million years (Ma). However, knowledge of its macroecological impact over prolonged time scales is limited. We show that marine ecosystems dominated by non-motile animals shifted to ones dominated by nektonic groups after the extinction. In Triassic oceans, animals at high trophic levels recovered faster than those at lower levels. The top-down rebuilding of marine ecosystems was still underway in the latest Triassic, ~50 Ma after the extinction, and contrasts with the ~5-Ma recovery required for taxonomic diversity. The decoupling between taxonomic and ecological recoveries suggests that a process of vacant niche filling before reaching the maximum environmental carrying capacity is independent of ecosystem structure building.

scholarly journals FRATs: Searching for fast radio transient in real-time with LOFAR

2012 ◽  
Vol 8 (S291) ◽  
pp. 233-233
Author(s):  
Heino Falcke ◽  
Keyword(s):  
Time Scales ◽  
Search Space ◽  
Large Field ◽  
New Radio ◽  
Wide Range ◽  
Imaging Observation ◽  
Previous Decade ◽  
First Results ◽  
Single Radio ◽  
Radio Transients

AbstractLOFAR is an innovative new radio interferometer operating at low radio frequencies from 10 to 270 MHz. It combines a large field-of-view, high fractional bandwidth, rapid response, and a wide range of baselines from tens of meters to thousand kilometers. Its use of phased-array technology and its digital nature make LOFAR an extremely versatile instrument to search for transient radio phenomena on all time scales. Here we discuss in particular the search for fast radio transients (FRATs) at sub-second time scales. In fact, at these time scales the radio sky is rather dynamic due to coherent emission processes. Objects like pulsars, flaring stars, or planets like Jupiter are able to produce bright short flares. For pulsars, most previous detection strategies made use of the rotation of pulsars to detect them, using Fourier techniques, but it is also possible to detect pulsars and other objects through their single pulses. Such surveys have, e.g., led in the previous decade to the detection of Rapid Radio Transients (RRATS), but the unprobed search space is still rather large. LOFAR is now conducting a rather unique survey over the entire northern sky, searching for bright dispersed single radio pulses. This FRATs survey makes use of the LOFAR transient buffer boards (TBBs), which had initially been used to detect nanosecond radio pulses from cosmic rays. The TBBs store the radio data from each single receiver element of LOFAR and allow one to look back in time. A trigger system that runs parallel to normal imaging observation allows one to detect single pulses in an incoherent beam of all LOFAR stations, covering several tens to hundred square degrees at once. Once triggered, the data can be used to localize the pulse and to discriminate cosmic sources from terrestrial interference through 3D localization. The system has been successfully tested with known pulsars and first results of the ongoing survey will be presented.

scholarly journals New Biochronological Scales of Planktic Foraminifera for the Early Danian Based on High-Resolution Biostratigraphy

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 479
Author(s):  
Ignacio Arenillas ◽  
Vicente Gilabert ◽  
José A. Arz
Keyword(s):  
High Resolution ◽  
Mass Extinction ◽  
Quantitative Data ◽  
Qualitative Data ◽  
Rapid Evolution ◽  
Planktic Foraminifera ◽  
Middle Latitudes ◽  
Evolutionary Radiation ◽  
Extinction Event ◽  
Mass Extinction Event

After the Cretaceous/Paleogene boundary (KPB) catastrophic mass extinction event, an explosive evolutionary radiation of planktic foraminifera took place in consequence of the prompt occupation of empty niches. The rapid evolution of new species makes it possible to establish high-resolution biozonations in the lower Danian. We propose two biostratigraphic scales for low-to-middle latitudes spanning the first two million years of the Danian. The first is based on qualitative data and includes four biozones: the Guembelitria cretacea Zone (Dan1), the Parvularugoglobigerina longiapertura Zone (Dan2), the Parvularugoglobigerina eugubina Zone (Dan3), and the Parasubbotina pseudobulloides Zone (Dan4). The latter two are divided into several sub-biozones: the Parvularugoglobigerina sabina Subzone (Dan3a) and the Eoglobigerina simplicissima Subzone (Dan3b) for the Pv. eugubina Zone, and the Praemurica taurica Subzone (Dan4a), the Subbotina triloculinoides Subzone (Dan4b), and the Globanomalina compressa Subzone (Dan4c) for the P. pseudobulloides Zone. The second scale is based on quantitative data and includes three acme-zones (abundance zones): the Guembelitria Acme-zone (DanAZ1), the Parvularugoglobigerina-Palaeoglobigerina Acme-zone (DanAZ2), and the Woodringina-Chiloguembelina Acme-zone (DanAZ3). Both biozonations are based on high-resolution samplings of the most continuous sections of the lower Danian worldwide and have been calibrated with recent magnetochronological and astrochronological dating.

scholarly journals The relationship between aerosol and cloud drop number concentrations in a global aerosol microphysics model

2009 ◽  
Vol 9 (1) ◽  
pp. 3207-3241 ◽  
Author(s):  
K. J. Pringle ◽  
K. S. Carslaw ◽  
D. V. Spracklen ◽  
G. M. Mann ◽  
M. P. Chipperfield
Keyword(s):  
Size Distribution ◽  
Cloud Droplet ◽  
Global Scale ◽  
Rate Of Change ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Percentage Error ◽  
Empirical Relationships ◽  
Wide Range ◽  
Global Mean

Abstract. Empirical relationships that link cloud droplet number (CDN) to aerosol number or mass are commonly used to calculate global fields of CDN for climate forcing assessments. In this work we use a sectional global model of sulfate and sea-salt aerosol coupled to a mechanistic aerosol activation scheme to explore the limitations of this approach. We find that a given aerosol number concentration produces a wide range of CDN concentrations due to variations in the shape of the aerosol size distribution. On a global scale, the dependence of CDN on the size distribution results in regional biases in predicted CDN (for a given aerosol number). Empirical relationships between aerosol number and CDN are often derived from regional data but applied to the entire globe. In an analogous process, we derive regional "correlation-relations" between aerosol number and CDN and apply these regional relations to calculations of CDN on the global scale. The global mean percentage error in CDN caused by using regionally derived CDN-aerosol relations is 20 to 26%, which is about half the global mean percentage change in CDN caused by doubling the updraft velocity. However, the error is as much as 25–75% in the Southern Ocean, the Arctic and regions of persistent stratocumulus when an aerosol-CDN correlation relation from the North Atlantic is used. These regions produce much higher CDN concentrations (for a given aerosol number) than predicted by the globally uniform empirical relations. CDN-aerosol number relations from different regions also show very different sensitivity to changing aerosol. The magnitude of the rate of change of CDN with particle number, a measure of the aerosol efficacy, varies by a factor 4. CDN in cloud processed regions of persistent stratocumulus is particularly sensitive to changing aerosol number. It is therefore likely that the indirect effect will be underestimated in these important regions.

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