Download The Oxygen Revolution as a premise to the rise of animal life

The Oxygen Revolution
as a premise to the rise of animal life
PAL = present-day O2 level in atmosphere = 0.2 atm
Oxygen rise between 2.5 and 2.0 By
Oxygen proxies:
1- MDF vs MIF of the S cycle
2- BIF vs redbeds
3- Uraninite - pyrite - siderite
4- The C cycle
5- Paleosols
The Sulphur cycle
Forms of Sulfur
Valences
-2
0
+2
+4
+6
O
X
I
D
A
T
I
O
N
R
E
D
U
C
T
I
O
N
Forms
Sulfides (Solfuri) H2S, FeS2
Elemental Sulfur S
Hyposulfites
Sulfites
Sulfates CaSO4, BaSO4
The Sulphur cycle
SO4
solfato
H2SO4
H2S
SO4
Oxidation of FeS2 => Hem+SO4; then H2S
SO2
SO4 solfato
batteri
H2S+Hem
FeS2
Solfuri
On modern Earth, the isotopes (e.g., 32S, 33S, 34S, 36S, or 16O, 17O, 18O, or
12C, 13C) are fractionated during eg biologic processes depeding on their mass in
accord with precise rules. Two types of mass-dependent
fractionation:equilibrium and kinetic
Normally, the product will be lighter than the reactant.
intuitive
example
Rain is enriched in 18O due to the equilibrium isotope effect as
18O has stronger bonds in H2Owater than H2Ovapour
Ad esempio nel passaggio di stato da H2Oaq ad H2Ovap: H2Ovap sarà più o
meno ricco di 16O rispetto all’acqua di partenza? Nella trasformazione da
liquido a gas l’acqua si arricchisce di 16O (diventa più negativa, più leggera)
per frazionamento cinetico. Nel ritrasformarsi in liquido (condensazione), la
pioggia prende 18O (più pesante) per frazionamento di equilibrio, poiché 18O ha
un legame più forte con H in H2Oaq. Il vapore rimanente è ancora più negativo.
1- MDF vs
MIF of the S
cycle
On modern Earth, the S
isotopes (32S, 33S, 34S,
36S) are fractionated
during eg biologic
processes depeding on
their mass in accord with
precise rules
Notations:
D33S = d33S - 0.515 d34S
D36S = d36S - 1.90 d34S
D33S, D36S = 0 in MDF
D33S, D36S ≠ 0 in MIF
Example of biologically mediated MDF of S:
Anaerobic bacterial sulfate reduction & sedimentary pyrite formation
Sulfate-reducing bacteria (e.g. Desulfovibrio or
Desulfotomaculum) are those bacteria that obtain their
energy by oxidizing organic compounds or molecular
hydrogen H2 while reducing sulfates to sulfides,
especially to hydrogen sulfide. In a sense, they
"breathe" sulfate rather than oxygen.
1. 2H+ + SO42- + 2(CH2O)->2CO2+H2S+2H2O+energy
2. Reaction of H2S with Fe+3 or Fe+2 mineral
4Fe2O3+9H2S ->8FeS+SO42-+8H2O+2H+
3. Formation of pyrite
FeS + S0 -> FeS2
Example of biologically mediated MDF of S:
Anaerobic bacterial sulfate reduction & sedimentary pyrite formation
Biological sulfate reduction shows a chemical preference for
32S (16 protons+16 neutrons) over the heavier isotopes 33S and
34S, resulting in sedimentary pyrite that is enriched in 32S
relative to gypsum formed from the same water body.
d33S biogenic pyrite less than d33S chemical gypsum
d34S biogenic pyrite much less than d34S chemical gypsum
In any case, the isotopic signature of gypsum and pyrite formed in
this way respond to MDF rules:
d33S = 0.515 d34S; D33S = 0 (i.e., the fractionation of 33S
relative to 32S is half the fractionation of 34S relative to 32S)
And also
d36S = 1.9 d34S; D36S = 0 (i.e., the fractionation of 36S relative
to 32S is twice the fractionation of 34S relative to 32S)
Example of physically mediated MIF of S:
Photodissociation of SO2 in atmosphere
No O2 in atmosphere = no ozone (O3) layer. UV-induced photodissociation
of volcanic SO2 generates isotopically distinct elemental sulfur (S0) and sulfur
trioxide (SO3) characterized by large anomalous (i.e., MIF) fractionations.
SO3 is soluble and reacts with water producing H2SO4, whereas elemental
sulfur is insoluble in surface waters. Therefore, these two components did not
mix, and their (positive and negative) MIF (D33S ≠0, D36S ≠0) signatures were
transmitted to mineral sulfides (FeS2) and sulfates (CaSO4) formed from them
in sedimentary environments.
H2SO4 + CaCO3 + 2H2O -> (CaSO4 · 2H2O) + CO2 + H2O Gypsum
H2SO4 + Ba(OH)2 -> BaSO4 + H2O Barite
FeS + S0 -> FeS2 Pyrite
Gypsum, Barite,
Pyrite with MIF
signatures D33S ≠0
D36S ≠0
Conclusions:
2- BIF
vs
redbeds
(…)
BIFs are composed of various iron rich
minerals:
Siderite (FeCO3) with reduced divalent
ferrous iron (Fe+2).
Magnetite (Fe3O4) with ferrous iron
(Fe+2) and oxidized trivalent ferric iron
(Fe+3).
Hematite (Fe2O3) with oxidized trivalent ferric
iron (Fe+3).
Notation: reduced
divalent ferrous iron
(Fe+2) is more soluble
than oxidized trivalent
ferric iron (Fe+3).
soluble Fe2+
accumulates in
seawater and at the
first fluctuation in O2,
it precipitates
massively as Fe3+ in
hematite forming BIFs
The Rajhara Iron Mine is situated approximately 90 km south of Durg in the Indian
state of Chhattisgarh and supplies iron ore (haematite). The orebody is a
Precambrian banded iron formation.
In an oxidizing atmosphere, iron
combines with oxygen to from
rustlike oxides. This leads to the
formation of redbeds instead of
BIFs
Red beds of the Moenkopi Formation, Utah
…an alternative scenario: disappearance of BIFs and deep ocean anoxia…
*
*) 4FeS2(pyrite) + 14O2 + 4H2O => 4Fe2+ 8SO4 + 8H+
3- Uraninite - pyrite - siderite
BIFs as recorders of incipient
oxidation of the atmosphere
Frimmel, H.E., 2005. Archaean atmospheric evolution:
evidence from the Witwatersrand goldfields,
South Africa. Earth-Science Reviews, 70: 37-41.
Pyrite grains in
conglomerate from the
Mississagi Formation
(Northern Ontario,
Canada) deposited in a
braided river at ca.
2.45-2.2 Ga. Note the
presence of rounded,
detrital pyrite grains
and euhedral (sharp
edged) pyrite grains
(red scale bar is 1 cm).
Detrital pyrite has been
interpreted to indicate
transport in a low
oxygen environment
(e.g., Frimmel, 2005).
Post-GOE mineral species incorporate one or more redoxsensitive elements that can occur in two or more oxidation states.
Thus, hundreds of new minerals incorporate iron (Fe2+ vs. Fe3+),
copper (Cu1+ vs. Cu2+), and uranium (U4+ vs. U6+), etc.
Hazen, mineral evolution
4- The C cycle
Organic matter and limestones that
accumulate on the present-day
ocean floor differ in their ratios of
13C and 12C by about 25 permil,
reflecting the fractionation of carbon
isotopes by photosynthetic algae
and cyanobacteria.
A similar difference of 25-30 permil
between d13Ccarb e d13Corg
existed down to ~2.2 By.
Before this time, things
were different…
Nature 290, 696-699 (23 April 1981)
Anomalous 13C depletion in early Precambrian graphites from
Superior Province, Canada
M. Schoell & F.-W. Wellmer
(…) Here we report the results of our measurements of samples of graphite
from the Archean of the Superior Province of Canada, one of which being
the most depleted in 13C ever found in the Precambrian.
Schoell and Wellmer discovered organic matter in lake beds ~2.8 By old that
was depleted in 13C by as much as 45 permil, a fractionation too large to be
ascribed to photosynthsis alone.
We need to invoke additional metabolisms
to explain Schoell and Wellmer data.
They explain this 13C depletion by
organisms in some areas living on
CH4 that has been formed by
methane-producing bacteria
in Precambrian stratified seas.
Photosynthesis alone cannot account for Schoell and Wellmer
(1981) results. They explained their results by
calling into action anaerobic methanogens and methane-eaters.
Methanogenic Archaea gain energy by breaking down organic
matter to methane.This methane is depleted in 13C.
Methane-eating bacteria gain energy from methane (CH4). In
doing so, they have preference for 12CH4 over 13CH4 and
fractionate methane by 20-25 permil.
Then, photosynthetic organisms + methane producing
Archaea + methane-eating bacteria can explain the unusual
isotopic values of Schoell and Wellmer (1981).
This interpretation implies the existence in ~2.8 By old
ecosystems of anaerobic metabolisms. No O2-respiring
organisms, no sulfate reducers. Therefore, low O2 levels at ~2.8
By (and higher levels by ~2.2 By when dC13 values are ‘normal’.
5- Paleosols
Especially relevant are the Hekpoort, Wolhaakop
and Drakenstein paleosols from South Africa
Rye and Holland found in soils older than 2.4-2.2 By that the iron
originally present in the underlying rocks was removed as the
soils formed. In contrast, iron in younger soils is retained. When
parent rocks weather under low O2 conditions, iron is released
as reduced soluble ferrous ions (Fe2+) and carried away by in
solution by oxygen-poor groundwaters. In contrast, once oxygen
increased, iron was immediately converted into insoluble iron
oxides (Fe3O4, Fe2O3) and remained in place (retained). [A.H.
Knoll, Life on a young planet, 2005]
2.24-2.20 By Hekpoort
Paleosol: less than 8x10-4
pO2
GOE
Notation: Today’s pO2
is 2x10-1 atm
2.2-2.0 By Drakenstein
Paleosol: 3x10-3 pO2
Summary
G.O.E.
Pre-G.O.E. ocean&atmosphere
was a place where 1) Sulphur was
fractionated mass-independently,
2) oceans were highly ferrous and
precipitated en-masse BIFs at
minimum O2 fluctuations, 3) U, Fe
and other minerals could exist
only in reduced forms (Uraninite,
Pyrite etc) and could not oxidize,
4) the d13C of organic matter was
highly negative (-45 per mil) and
reflective of anaerobic metabolic
processes involving mathanogens
and methane eaters, 5) paleosols
were highly depleted in soluble
Fe2+
Post-G.O.E. ocean&atmosphere
was a place where 1) Sulphur was
fractionated mass-dependently, 2)
no Fe2+ dissolved in oceans, 3) all
Fe2+ readily oxidized to Fe3+
forming hematitic rust in redbeds,
4) U, Fe and other minerals could
oxidize, forming a variety of new
minerals, 5) the d13C of organic
matter reflected fractionation by
photosynthesis, 6) paleosols
retained Fe2+ in magnetite and
contained also Fe3+ in hematite
Open questions:
1- when did the G.O.E. ‘exactly’ occur (within the broad
time window comprised between 2.5 and 2.0 Ga)?
Last results from the S cycle
2- how large was it with respect to present-day
Oxygen level (0.2 atm)?
3- what caused it?
Time is everything. When did the G.O.E. occur?
The youngest sediments with a strong
MIF signal is 2.47-Gyr-old Dales Gorge
Member, Western Australia (Farqhar et
al., 2000; see previous slides).
The oldest sediments with a small or no
MIF signal is 2.32-Gyr-old Rooihoogte
Formation (Bekker et al., 2004).
G.O.E. between 2.47 and 2.32 Gy
…possibly close to 2.32 Gy…
How large was the G.O.E.?
The G.O.E. produced apparently a very rapid rise of
oxygen from less than 0.001% of PAL to 1-40%
PAL between 2.47 and 2.32 Gy (early Paleoproterozoic). The rest of O2 was added later, at
~0.635-540 Gy (Ediacara-early Phanerozoic
time)
Notation: PAL
is 2x10-1 atm
A two step or multi-step model?
What caused the G.O.E.?
A change in style of volcanism or the rise of photosynthesis?
…or perhaps an increase in organic carbon burial?
A change in
style of
volcanism
A
P
A change in
style of
volcanism
A change in
style of
volcanism
CH4 + 2 O2 = CO2 + 2 H2O
2 H2S + 3 O2 = 2 SO2 + 2 H2O
A change in
style of
volcanism
Photosynthesis
Recall that G.O.E. seems to have occurred between 2.47 and 2.32 Gy
…possibly close to 2.32 Gy, which is the age of the Makganyene SE
Kirschvink & Kopp 2008
CAUSE OF GOE
Burial of Organic Matter?
The anomalous carbon isotope behaviour of the
Lomagundi excursion is tied to intense burial
of organic matter
Links btw GOE, LIPs & Snowball Earth
~2.45 Gy supercontinent and Ongeluk LIP
Gumsley et al. 2017
Paleoproterozoico
GOE, LIPs & Snowball Earth
Large juvenile volcanic provinces on extensive low-latitude continental
landmasses are likely to have enhanced chemical weathering of aerially
extensive, nutrient-rich continental flood basalts.
This weathering resulted in enhanced flux of phosphorus and other essential
nutrients onto extensive continental margins and into intracratonic basins.
An enhanced nutrient flux would have greatly increased photosynthetic
activity and oxygen production, temporally linked to higher net burial of
organic carbon in accumulating sediments.
An incipient rise of free atmospheric oxygen would have led to rapid oxidation
of atmospheric methane forcing catastrophic climate change and plunging
Earth into a global glaciation (Huronian/Makganyene Paleoproterozoic
Snowball Earth).
Extra nutrients delivered to oceans during Snowball Earth deglaciation would
have sustained photosynthetic activity and oxygen production ->GOE.
The Neoproterozoic Oxygenation Event (NOE)
The Neoproterozoic Oxygenation Event (NOE)
The Neoproterozoic Oxygenation Event (NOE)
Evidence from Molibdenum (Mo) and Vanadium (V)
Sahoo et al. (2012)
In today’s predominantly oxygenated oceans, Mo and V are abundant and
have long residence times (Mo = 800–440 kyr; V = 50 kyr), much longer
than the ocean mixing time (1.5 kyr), and hence at any local place they track
global seawater composition.
Mo and V exit the water column in black shales
forming in reducing marine environments (e.g., Black Sea).
The magnitude of Mo and V enrichments in black shales reflect dissolved Mo
and V concentrations in seawater
The observed Mo and V enrichments in lower Doushantuo
Formation black shales suggest that oxic waters bathed the
vast majority of the ocean.
Oxygen-deficient conditions must have been spatially limited
and only located where high organic matter loading caused
oxygen depletion along ocean margins
CAUSE OF NOE: Burial of Organic Matter?
Extreme variations in the carbon isotopic record
are characteristic of later Neoproterozoic times:
(1) an exceptionally long lived positive
δ13Ccarb excursions after c. 800 Ma has been
interpreted to represent increased organic
carbon burial and hence, a release of oxidizing
power into the Earth's surface environment;
while (2), the extremely negative δ13Ccarb
excursion in the mid-Ediacaran suggests the
oxidation of a very large organic carbon
pool, possibly due to enhanced ocean cycling
and resultant deep ocean ventilation.
The extreme mid-Ediacaran excursion is
consistent with the hypothesis that atmospheric
oxygen rose significantly after ca. 550 Ma, and
contemporaneous with diversification of
macroscopic metazoans at the end of the
Ediacaran Period.
In addition, the overall increase in 87Sr/86Sr
ratio in marine sediments through the
Neoproterozoic and into the Cambrian indicates
a rise in chemical weathering and nutrient
supply to the ocean which might have increased
primary production including photosynthesizing
cyanobacteria and enhanced the rates of
organic carbon burial.
Evolution of seawater 87 Sr/ 86 Sr since the last
70 My. Intense chemical weathering in the
Himalaya is suggested as a potential
cause for the steady increase in 87 Sr/ 86 Sr
since 40 My (Raymo and Ruddiman 1992).
Links btw NOE, LIPs & Snowball Earth
NOE, LIPs & Snowball Earth
~0.715 Gy Rodinia supercontinent and Franklin LIP
Neoproterozoico
NOE, LIPs & Snowball Earth
Large juvenile volcanic provinces on extensive low-latitude continental
landmasses are likely to have triggered near-equatorial glaciations via
enhanced chemical weathering of aerially extensive, nutrient-rich
continental flood basalts.
This weathering resulted in increased carbon dioxide drawdown and onset of
glaciation (Sturtian-Marinoan Neoproterozoic Snowball Earth), and an
enhanced flux of phosphorus and other essential nutrients onto extensive
continental margins and into intracratonic basins.
An enhanced nutrient flux would have greatly increased photosynthetic
activity and oxygen production, temporally linked to higher net burial of
organic carbon in accumulating sediments.
Extra nutrients delivered to oceans during Snowball Earth deglaciation would
have sustained photosynthetic activity and oxygen production ->NOE.
Ediacara !