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MGS-2
PR98-1
89-MC-1
GF-3
MGS-8
m
200
MGS-7
100
0
Euxinic
Transitional
Ferruginous
-100
-200
Figure 9.4. Development of ocean chemistry through the transition from the gunflint Iron
Formation (the Biwabik offshore) to the overlying rove Formation (the Virginia Formation
offshore). time moves upwards in the plot (younger sediments on top) and we move further
offshore in going from left to right. Figure reproduced from Poulton et al. (2010).
of evidence for deep-water ferruginous conditions as well. And ferrugi-
nous conditions can be found all the way until the time when animals
first evolved some 1.3 billion years later. We'll look at when animals
make an appearance in the next chapter, but let's reflect on where we
stand relative to the original Canfield Ocean model. After the GOE, the
deep ocean appears to have remained largely anoxic as the model pre-
dicted, and sulfidic conditions were more extensive as the model also
suggested. However, these sulfidic conditions were not particularly
extensive. Instead, ferruginous conditions seemed to dominate in the
anoxic ocean.
If ferruginous conditions dominated, why then are BIFs exceedingly
rare during this time in Earth history, as we saw graphically in igure
9.2? Good question. I believe that the original Canfield Ocean model
 
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