On 12/30/23 09:37, erik simpson wrote:
Distinctive microfossil supports early Paleoproterozoic rise in complex cellular organisation
Abstract
The great oxidation event (GOE), ~2.4 billion years ago, caused
fundamental changes to the chemistry of Earth's surface environments. However, the effect of these changes on the biosphere is unknown, due to
a worldwide lack of well-preserved fossils from this time. Here, we investigate exceptionally preserved, large spherical aggregate (SA) microfossils permineralised in chert from the c. 2.4 Ga Turee Creek
Group in Western Australia. Field and petrographic observations, Raman spectroscopic mapping, and in situ carbon isotopic analyses uncover
insights into the morphology, habitat, reproduction and metabolism of
this unusual form, whose distinctive, SA morphology has no known
counterpart in the fossil record. Comparative analysis with microfossils from before the GOE reveals the large SA microfossils represent a
step-up in cellular organisation. Morphological comparison to extant micro-organisms indicates the SAs have more in common with coenobial
algae than coccoidal bacteria, emphasising the complexity of this microfossil form. The remarkable preservation here provides a unique
window into the biosphere, revealing an increase in the complexity of
life coinciding with the GOE.
https://onlinelibrary.wiley.com/doi/10.1111/gbi.12576
I am thinking that did not instantaneously happen all
at once 2.4 billion years ago.
To the best of my understanding, I am thinking that most
of the world's iron ore deposits happened because iron is
much more soluble in water under conditions where carbon
dioxide is dissolved in the water in great amounts rather
than at a different ratio than what you would expect if
there were significant amounts of oxygen in the atmosphere
and much less carbon dioxide.
The starvation of some metal ions dissolved in the ocean
now for the production of organisms, which might be at
the bottom of the ocean kilometers deeper than the photic
zone near the top of the ocean, may be somewhat of a
limiting factor for life in the oceans now. Shallow
waters with somewhat more or less dissolveable particles near
the top sunlight layer tend to be more productive for life
and the microscopic photosynthetic algae that is
the basis of the food chain in the oceans often in
comparison with many deeper open waters.
In essence, iron had to precipitate out of the ocean before
the atmosphere could convert from carbon dioxide to oxygen
and nitrogen, and a lot of iron ore deposits date from as
recent as one and a half billion years ago. That is almost
a billion more recent than 2.4.
In general however, of course, oxygen producing photosynthesis
would have to be able to exist to BEGIN the process, so the start
of it might therefore of course be earlier.
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