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End-Permian and end-Triassic extinctions



From: Ben Creisler
bcreisler@gmail.com


An article and some news items about the mass extinctions at the end
of the Permian and the end of the Triassic.


Carlo Romano, Nicolas Goudemand, Torsten W. Vennemann, David Ware,
Elke Schneebeli-Hermann, Peter A. Hochuli, Thomas Brühwiler, Winand Brinkmann
& Hugo Bucher (2013)
Climatic and biotic upheavals following the end-Permian mass extinction.
Nature Geoscience 6:57–60
doi:10.1038/ngeo1667
http://www.nature.com/ngeo/journal/v6/n1/full/ngeo1667.html



Recovery from the end-Permian mass extinction is frequently described
as delayed, with complex ecological communities typically not found in
the fossil record until the Middle Triassic epoch. However, the
taxonomic diversity of a number of marine groups, ranging from
ammonoids to benthic foraminifera, peaked rapidly in the Early
Triassic. These variations in biodiversity occur amidst pronounced
excursions in the carbon isotope record, which are compatible with
episodes of massive CO2 outgassing from the Siberian Large Igneous
Province. Here we present a high-resolution Early Triassic temperature
record based on the oxygen isotope composition of pristine apatite
from fossil conodonts. Our reconstruction shows that the beginning of
the Smithian substage of the Early Triassic was marked by a cooler
climate, followed by an interval of warmth lasting until the Spathian
substage boundary. Cooler conditions resumed in the Spathian. We find
the greatest increases in taxonomic diversity during the cooler phases
of the early Smithian and early Spathian. In contrast, a period of
extreme warmth in the middle and late Smithian was associated with
floral ecological change and high faunal taxonomic turnover in the
ocean. We suggest that climate upheaval and carbon-cycle perturbations
due to volcanic outgassing were important drivers of Early Triassic
biotic recovery.

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Did methanogen microbes contribute to Permian extinction?
http://www.newscientist.com/article/mg21628954.400-permian-mass-extinction-triggered-by-humble-microbe.html
http://www.uvm.edu/~cmplxsys/?Page=newsevents/2012fall/d-rothman.php&SM=newsevents/_newseventsmenu.html

=

Richard Kerr (20120
Tying Megaeruptions to a Mass Extinction Long After the Fact.
Science 338(6114): 1522-1523
DOI: 10.1126/science.338.6114.1522-b
http://www.sciencemag.org/content/338/6114/1522.2.summary


To incriminate a global catastrophe in the extinction of a wide swath
of the biosphere, you need precise dates for two events: the
catastrophe—say, an asteroid impact or volcanic eruption—and the mass
extinction. At the meeting, geochronologists who measure the passage
of time in the steady ticking of radioactive decay presented
convincing evidence, using impressively precise dating, that massive
eruptions at the opening of the Atlantic Ocean 201 million years ago
drove the mass extinction that cleared the way for the rise of the
dinosaurs.