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(a)
(b)
(c)
(d)
Marine
microfauna
Rajahmundry
beds
+ 300,000 years
+ 50,000 years
KTB
Dinosaur and
mammal teeth
- 20,000 years
Fish and frogs
- 400,000 years
Ancient ray (fish)
Dinosaurs
Magnetic
polarity
A. mayaroensis
Volcanic intensity
in Deccan traps
Figure 15.1 A synthesis of paleomagnetic, paleontologic and geochronologic
data from the Deccan Traps (as updated in Courtillot, 1999 ). (a) Proposed changes
in volcanic intensity; (b) magnetic polarity; (c) geological section of the Deccan;
(d) key fossils.
largest volcanic catastrophes in the last 200 Ma , leading us to conclude, our
hypothesis that the Deccan eruptions should be linked to the KTB and must be
accounted for by KTB scenarii may eventually allow tests of
'
internal
'
vs.
'
external
'
models for this major geological event
. Recalling the effects of the 1783 eruption of
Laki in Iceland, Courtillot et al. ( 1986b ) suggested that
It would be interesting to test
whether the Deccan lavas were unusually rich in sulfur, and to model the injection of
S in the atmosphere related tomore than 10 6 km 3 of lava erupted over less than 1Ma
.
This was the start of our involvement in the volcanism/extinction connection.
McElhinny ( 1968 ) and Kono et al .( 1972 ) had already used paleomagnetic
reversals to argue for an upper value of 3 to 5 Myr for the duration of volcanism.
McLean ( 1981 ) proposed the
first climatic scenario of the consequences of volcan-
ism based on a massive injection of CO 2 .Of
cer and Drake ( 1985 ) argued that
the KTB events must have lasted 10 to 100 kyr rather than the mere instant of the
impact and linked this to Deccan volcanism. For several years, proponents of
the impact scenario were pitted against proponents of a volcanic scenario.
We complemented our work on the Deccan and produced a short summary for
the general public (Courtillot, 1990 ). A more technical review with new results
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