Geoscience Reference
In-Depth Information
Cambrian-Ediacaran
Boundary
glacial intervals
9
6
3
0
-3
-6
-9
Shuram-Wonoka anomaly
-12
500
600
700
800
900
1000
Age (millions of years)
Figure 10.4. neoproterozoic record of inorganic carbon isotope distribution. the shuram-
wonaka anomaly is indicated as well as the major episodes of glaciation. the relationship
of the shuram-wonaka anomaly to glaciation (it could well come after) as well as the length
of the anomaly are highly uncertain. Data compiled and kindly made available by galen
Halverson of mcgill University and matt saltzman from Ohio state University.
to this problem, including an ingenious proposition by Dan Rothman
from MIT. He imagined that at this time in Earth history, the ocean was
much like an organic soup, containing huge concentrations of dissolved
organic matter. Dissolved organics should have the same 13 C- depleted
isotopic signal of algae as we explored in previous chapters. Dan argued
that the occasional oxidation of this organic soup produced a huge
amount of 13 C- depleted CO 2 . Indeed, Dan argued that enough 13 C- CO 2
could be produced to give us the Shuram-Wonoka anomaly. This is
a  brilliant idea, but I've never quite understood how this oxidation
episode was started. For this and other reasons, Christian Bjerrum and
I have proposed another solution involving the oxidation of a huge
methane pool (containing even more 13 C-depleted carbon than dis-
solved organics), which you can read more about if you follow this
endnote. 14 In any event, understanding the Shuram-Wonoka anomaly
requires some lateral thinking, but these solutions all come with a cost,
at least in terms of oxygen. So, whether we're talking about the oxida-
tion of dissolved organics or methane to form the Shuram-Wonoka 13 C
 
 
Search WWH ::




Custom Search