Earth Sciences 2240F/G Lecture Notes - Lecture 18: Siberian Traps, Large Low-Shear-Velocity Provinces, Zircon
11 Jun 2018
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Chapter 18- End Permian Mass Extinction
1.0 Introduction
• end of Permian 251.4 mya
• signifies the most catastrophic mass extinction ever
• “earth came very close to losing life completely”
• 96% of marine and 70% of terrestrial species died in less than 1
my
• even insects…
• a period of gradual deterioration followed by a catastrophic event
• cause/causes global
2.0 Dating the Extinctions
• prior to 2004, time and duration of old event speculated bc rocks of
this age too modified to yield accurate data
• however patch of pristine rocks in southern China and Greenland
proved well
• mineral zircon (found sparingly in many volcanic sequences)
contain small amounts of Ur
o Ur radioactively decay along well known time path to lead,
leading to zircon crystals being accurately age dated
rocks in China sequence date Permian-Triassic
boundary catastrophic extinction at 251.4 +/- 0.3
mya
o all major extinctions clustered around that one dated peak,
few gradual extinctions prior, and a few later, but whole time
was short, between 0.72-1.22 my
• by looking at rocks in Greenland, see animals died over a period of
10-60 thousand years
o plant life took several hundred thousand years to go through
whole extinction process
3.0 Setting the Scene
• Pangaea all together and early Permian the supercontinent spanned
from almost the North Pole to a good section over the South
• Dry winds blew, dry and hot summers and dry and cold winters
• Great diversity of life, the density of populations lower
• Finals stages had two flood basalt events
o First was over a plume beneath China
o Second developed over superplume in Siberia (Siberian
Traps)
▪ Date at 251.2 +/- 0.3 mya (before end of Permian)
▪ As much as 20% might have been explosive, potentially
large quantities of ash and sulphur aerosols could have
been tossed into upper atmosphere
▪ May have been time to allow highly acidic precipitation
to develop from aerosols
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