1
Supporting
Information for
Reconciling Archean organic
-rich mudrocks with low primary
productivity before the Great Oxygenation Event
Noam Lotem
1
*, Birger Rasmussen
2
, Jian-
Wei Zi
3
, Sarah S. Zeichner
1
, Theodore M. Present
1
,
Yinon M.
Bar
-On
1
, Woodward W. Fischer
1
.
1
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA
91125, USA.
2
School of Earth Sciences, The University of Western Australia, Nedlands, WA 6009, Australia.
3
John de Laeter Centre, Curtin University, Bentley, WA 6102, Australia.
*Corresponding author
: Noam Lotem
Email:
nlotem@caltech.edu
This PDF file includes:
Supporting t
ext
Figures
S1
to
S3
Tables S1
to
S6
Legends for Datasets S1 to S3
SI
References
Other supporting
materials for this manuscript include
the following:
Datasets S1 to S
3
2
Supporting
Information Text
Modeling total organic carbon (TOC) as a function of sedimentation rate
To understand and quantify the processes leading to the differences between the
Archean and
Phanerozoic TOC data sets, we developed a model that predicts the TOC concentration for a
given sedimentation rate, considering the delivery flux of organic carbon (OC) and the O
2
exposure time (1)
. Generally, our model is logically similar to previous model approaches (2, 3)
.
The TOC concentration of the initially deposited surface sediments was calculated by Eq. S1 (the
OC delivery flux is an adjustable parameter).
Eq. S1.
푇푇푇푇퐶퐶
푖푖푖푖푖푖푖푖푖푖푖푖푖푖
�
푔푔
푐푐푚푚
3
�
=
푂푂푂푂
푑푑푑푑푖푖푖푖 푑푑푑푑푑푑푑푑
푓푓푖푖푓푓푓푓
�
푔푔
푐푐푚푚
2
푦푦푦푦
�
푠푠푑푑푑푑푖푖푚푚푑푑푖푖푖푖푖푖푖푖푖푖
푠푠푖푖
푑푑푖푖푖푖푑푑
�
푐푐푚푚
푦푦푦푦
�
O
2
exposure time was calculated by Eq. S2, following
(4)
(the O
2
penetration depth is an
adjustable parameter)
.
Eq. S2.
푇푇
2
푒푒푒푒푒푒
.
푡푡푡푡 푚푚푒푒
=
푂푂
2
푝푝푑푑푖푖푑푑푖푖푑푑푖푖푖푖푖푖푠푠푖푖
푑푑푑푑푝푝푖푖 ℎ
푠푠푑푑푑푑푖푖푚푚푑푑푖푖푖푖푖푖푖푖푖푖
푠푠푖푖
푑푑푖푖푖푖푑푑
The aerobic remineralization of organic carbon was estimated as a first order rate law, yielding an
exponential decay of the TOC concentration with time. Therefore, the TOC buried beneath the O
2
penetration depth (TOC
anoxic
) was calculated by Eq. S3, while
k
represents the first
-order rate
constant of the remineralization reaction (tunable parameter), and
t
is the
O
2
exposure time.
Eq. S3.
푇푇푇푇퐶퐶
푖푖푖푖푠푠푓푓푖푖푐푐
=
푇푇푇푇퐶퐶
푖푖푖푖푖푖푖푖푖푖푖푖
∙푒푒
−푘푘푖푖
,
푡푡
=
푇푇
2
푒푒푒푒푒푒
.
푡푡푡푡 푚푚푒푒
The anaerobic remineralization was expressed as the anoxic zone burial efficiency (BE
anoxic
,
tunable parameter). This parameter describes the fraction of TOC that is preserved from the
overall TOC that enters the anoxic sediment zone (Eq. S4).
Eq. S4.
푇푇푇푇퐶퐶
푏푏푓푓푑푑푖푖푑푑푑푑
=
퐵퐵퐸퐸
푖푖푖푖푠푠푓푓푖푖푐푐
∙푇푇푇푇퐶퐶
푖푖푖푖푠푠푓푓푖푖푐푐
The last step converts the TOC units to weight percentages, using the sediment density (Eq. S5).
Eq. S5.
푇푇푇푇퐶퐶
푤푤푖푖
%
=
푇푇푂푂푂푂
푏푏푏푏 푦푦푡푡푒푒 푏푏
�
푔푔
푐푐푚푚
3
�
푠푠푑푑푑푑푖푖푚푚푑푑푖푖푖푖
푑푑푑푑푖푖푠푠푖푖푖푖 푑푑
�
푔푔
푐푐푚푚
3
�
∙
100%
The values substituted for the tunable parameters were based on
prior studies for the
Phanerozoic model (Table S
2), while for the Archean model the OC delivery flux and O
2
penetration depth were adjusted to fit the Archean data, according to different hypothetical
scenarios (Table S
4).
Our model predictions also considered an empirical term that describes the typical persistence of
TOC at very low concentrations (<0.1 wt. %) that remain constant with depth in oligotrophic
oxygenated sediments, regardless of the electron acceptor availabi
lity
(5)
. Thus, for low
sedimentation rates that undergo long O
2
exposure times, the TOC may remain at 0.1% (Fig. 2
A).
3
Model sensitivity analyses
To examine the sensitivity of the model to its tunable parameters, we tested a wide range of
values for all adjustable parameters
—organic carbon delivery flux, the O
2
penetration depth, the
first
-order rate constant for aerobic decomposition of TOC, the burial efficiency in the anoxic
sediment zone, and the sediment density. The results for variations in O
2
penetration depth are
presented in Figure 2 and discussed in the main text, while the supplementary section focuses on
all other parameters (For all supplementary simulations O
2
penetration depth remains 1 mm).
Overall, substantially modifying the tunable parameters over values that are relevant for modern
basins cou
ld not explain the Archean data, with the exception of the rate constant for aerobic
TOC decomposition (Fig. S2).
The sensitivity of the model to changes in the delivery flux of organic carbon to the sediment was
tested in the range of 0.31 to 320 gC m
-2
y
-1
, while the value applied for the Phanerozoic model
was 20 gC m
-2
y
-1
. Changes in delivery flux had a substantial effect on the TOC concentrations
predicted by the model, but the TOC maximum point remains corresponding to the same
sedimentation rate. Generally, increasing the delivery flux may “stretch” the diagram, but the
underlying nature of the TOC
-sedimentation
rate relationship is preserved (Fig. S2A
).
The effect of modifying of the first
-order rate constant for aerobic decomposition of TOC in the
range 6.25×10
-6
to 8×10
-4
day
-1
was examined, while the value applied in all models was 5×10
-5
day
-1
(Fig. S2
B). Variations in the rate constant are mathematically equivalent to changes in O
2
exposure time, thus they modify model predictions similarly to changes O
2
penetration depth (as
O
2
exposure time is a linear function of its penetration depth) (Fig.
2A and S2B
). Therefore, the
Archean data could be explained both by extremely low O
2
penetration depths (<0.25 mm), as
demonstrated in the anoxic scenario (O
2
penetration= 0 mm, Fig
. 2C
and 3D
), or an alternative
scenario of much slower aerobic decomposition of organic matter
(Fig.
S2B)
. To account for
Mount McRae and Jeerinah data, the decomposition rate constant would need to have been 4 to
8-folds lower than the Phanerozoic
/modern (Fig. S2
B). This scenario would require a substantial
change in biomass composition or the efficiency of enzymes through time. Alternatively, the lower
decomposition rates could be attributed to anaerobic flavors of respiration with
alternative
electron acceptors sourced from the water column, such as iron oxide phases. In this case, the
model represents pervasive anoxia, but unlike the
dilution
-controlled model (Fig.
2C and 3D
), the
decomposition of organic matter is limited by the availability of an electron acceptor that
originates either in the water column or delivered with the sediment, and its penetration depth (or
depth of activity) is limited. However, both the slower a
erobic decomposition scenario and the
alternative anaerobic depth
-limited respiration case (which are mathematically equivalent in our
model), failed to capture the distribution of TOC in the Archean rock record anywhere as
accurately as the dilution-
contr
olled anaerobic model (Fig. S
3). This also support
s the idea that
dilution by inorganics, and not electron acceptor availability, was the main factor controlling TOC
concentrations in Archean rocks, in agreement with studies that suggested the main TOC
decomposition pathways in the Archean were fermentatio
n and methanogenesis
(6, 7)
.
Variations in the anoxic sediment zone burial efficiency and the sediment density had only minor
effects on model predictions. Modifications in anoxic sediment zone burial efficiency ([TOC
preserved in rock]/[TOC entering the anoxic zone]) were tested in t
he range of 6.25% to 100%,
while the value applied in
our
models was 50%. As changes in anoxic burial efficiency are
mathematically equivalent to changes in delivery flux, the TOC variations for burial efficiencies of
12.5% to 100% are within an order of m
agnitude (Fig. S2C). The sensitivity to sediment density
was examined for densities of 1.5 to 3 g cm
-3
, inducing a 2-
fold variation in TOC concentrations
(Fig. S2
D). The value applied in all models was 2.7 g cm
-3
.
4
Explaining
the anaerobic
, dilution
-controlled trend
In the absence of O
2
, under a constant delivery flux of organic carbon, changes in sedimentation
rate are effectively equivalent to changes in the amount of inorganic input, diluting/condensing the
TOC concentrations. In this case, the predicted relationship between TOC conce
ntrations and
sedimentation rates appears as a -
1 slope on a log-
log scale, following the power
-law relationship
y = x
-1
(Eq. S6
-S9). It is also important to note that in our model, the anoxic burial efficiency is
considered independent
of the sedimentation rate (based on examples like those observed by
(8)
; Eq. S4
), preserving the initial power
-law relationship and allowing the predicted TOC
concentrations to be controlled exclusively by the extent of dilution by inorganics
(Fig. 2C and
3D)
.
Eq. S6.
푇푇푇푇퐶퐶
푖푖푖푖푖푖푖푖푖푖푖푖푖푖
=
푂푂푂푂
푑푑푑푑푖푖푖푖 푑푑푑푑푑푑푑푑
푓푓푖푖푓푓푓푓
푠푠푑푑푑푑푖푖푚푚푑푑푖푖푖푖푖푖푖푖푖푖푠푠
푖푖
푑푑푖푖푖푖푑푑
Is equivalent to:
푦푦
=
푖푖
푓푓
,
푎푎
=
푐푐푐푐푐푐푐푐 푡푡푎푎푐푐 푡푡
Taking the logarithm of both sides of the equation:
Eq. S7.
log
(
푦푦
) =
−
log
(
푥푥
)
+
log
(
푎푎
)
Thus, the TOC appears as a power
-law
function of
the
sedimentation rate with a slope of -
1 on a
log
-log scale.
An alternative way to describe the dilution effect is to consider masses of organic and inorganic
sediment, instead of the organic carbon flux and the total (inorganic + organic) accumulation rate
of height (i.e., sedimentation rate). In this case, the dilution by inorganics can be described by Eq.
S8.
Eq. S8.
푇푇푇푇퐶퐶
=
푠푠푑푑푔푔푖푖푖푖푖푖푐푐
푖푖푖푖푠푠푑푑푔푔 푖푖푖푖푖푖 푐푐+푠푠푑푑푔푔푖푖푖푖푖푖푐푐
, corresponding to:
푦푦
=
푖푖
푓푓+푖푖
,
푎푎
=
푐푐푐푐푐푐푐푐 푡푡푎푎푐푐 푡푡
If
푎푎 ≪푥푥
,
푥푥
+
푎푎
≈푥푥
Taking the logarithm of both sides of the equation:
Eq. S9.
log
(
푦푦
)
≈
−
log
(
푥푥
)
+
log
(
푎푎
)
Therefore, Eq. S8 is approximately a power
-law function with an apparent -
1 slope on a log-
log
scale, when the organic input is significantly lower than the inorganic input, which is a common
case in sedimentary basins.
5
Fig. S1.
Tera
-Wasserburg concordia
plot for zircon in tuff band from drill
-hole DDH186 (drill
-depth
203.5 m). Datapoint error ellipses are 68.3% confidence.
6
Fig. S2
.
Phanerozoic model sensitivity analyses. Gray lines represent model results for variations
in tunable parameters, yellow lines represent the chosen values that were applied in the
Phanerozoic model (Fig. 2). (
A
) Varying the delivery flux of organic carbon to the sediment
surface, in 4-
fold increase increments from 0.31 to 320 gC m
-2
y
-1
, while the value applied was 20
gC m
-2
y
-1
. (
B
) Varying the first
-order rate constant for aerobic decomposition of TOC in 2-
fold
increase increments, from 6.25*10
-6
to 8*10
-4
day
-1
, the value applied in all models was 5*10
-5
day
-1
. (
C
) Varying the anoxic sediment zone burial
efficiency ([TOC preserved in rock]/[TOC
entering the anoxic zone]) a in 2-
fold increase increments, from 6.25% to 100%, while the value
applied was 50%. (
D
) Varying the sediment density from 1.5 to 3 g cm
-3
in increments of 0.5 g
cm
-3
, the value applied in all models was 2.7 g cm
-3
. For all simulations, the O
2
penetration depth
remained 1 mm. Blue circles and red triangles represent Phanerozoic and Archean data,
respectively (area shaded in red represents Archean 68% confidence interval for sedimentation
rate).
7
Fig.
S3. Comparing the TOC distributions predicted by the slow TOC decomposition model
and the anaerobic dilution
-controlled model, with a data compilation of Archean rocks.
(
A
)
A rank order plot of the TOC concentrations predicted by the slow TOC decomposition model
(orange
dots) and the anaerobic dilution-
controlled model (purple dots). (
B
) A rank order plot of a
data compilation of measured TOC of Archean rocks (
n
= 1992). The area shaded in gray
represents the range of TOC values from Jeerinah and Mount McRae shales.
8
Table S
1.
SHRIMP U
-Pb data for zircon in tuff bed intersected in drill hole DDH186 at 203.5 m.
Analysis
No.
U
(ppm)
Th
(ppm)
Th/U
f
206
(%)
To t a l
238
U
/
206
Pb
±1σ
To t a l
207
Pb
/
206
Pb
±1σ
238
U
/
206
Pb
*
±1σ
207
Pb
*
/
206
Pb
*
±1σ
Disc. (%)
207
Pb
*
/
206
Pb
*
Age (Ma)
±1σ
Group 1 data
(
f
206
<1%, disc. <5%)
BR21
-
08K.3
-
3
474
290
0.63
0.06
1.98
0.04
0.1874
0.0016
1.98
0.04
0.1868
0.0016
+3
2715
14
BR21
-
08K.2
-
1
558
337
0.62
0.13
1.97
0.03
0.1862
0.0015
1.97
0.03
0.1851
0.0016
+3
2699
15
BR09
-
20M.2
-
1
274
130
0.49
0.64
1.99
0.05
0.1898
0.0017
2.00
0.05
0.1841
0.0022
+4
2690
20
BR09
-
20J.1
-
1x
375
242
0.67
0.04
1.91
0.04
0.1843
0.0013
1.91
0.04
0.1839
0.0013
-
1
2689
12
BR09
-
20L.1
-
1x
332
187
0.58
0.34
1.94
0.04
0.1859
0.0031
1.94
0.04
0.1829
0.0033
+0
2679
29
BR21
-
08G.2
-
3
499
313
0.65
0.07
2.00
0.03
0.1833
0.0016
2.00
0.03
0.1827
0.0016
+3
2678
15
BR09
-
20J.1
-
1
574
382
0.69
0.12
2.03
0.04
0.1838
0.0013
2.03
0.04
0.1828
0.0014
+4
2678
12
BR21
-
08I.1
-
2
354
212
0.62
0.49
1.94
0.03
0.1864
0.0017
1.95
0.03
0.1820
0.0021
+0
2671
19
BR21
-
08J.3
-
2
486
253
0.54
0.22
1.87
0.03
0.1838
0.0015
1.87
0.03
0.1819
0.0017
-
4
2670
15
BR21
-
08G.2
-
1
491
334
0.70
0.97
1.92
0.03
0.1898
0.0016
1.93
0.03
0.1812
0.0023
-
1
2664
21
BR09
-
20I.1
-
1
451
284
0.65
0.62
1.90
0.04
0.1862
0.0013
1.91
0.04
0.1807
0.0017
-
2
2659
15
BR21
-
08G.2
-
2
472
320
0.70
0.79
2.05
0.04
0.1854
0.0016
2.06
0.04
0.1784
0.0022
+4
2638
21
Group 2 data
(
f
206
= 1.0
-
1.3%, disc. <5% or
f
206
<1%, disc. = 5
-
9%)
BR09
-
20M.1
-
1
402
218
0.56
0.09
2.07
0.05
0.1869
0.0015
2.08
0.05
0.1860
0.0016
+8
2707
14
BR21
-
08J.3
-
1
462
335
0.75
1.20
1.89
0.04
0.1965
0.0034
1.91
0.04
0.1858
0.0040
-
1
2705
35
BR21
-
08K.3
-
4
485
258
0.55
0.04
2.12
0.06
0.1850
0.0017
2.12
0.06
0.1846
0.0018
+9
2695
16
BR09
-
20I.1
-
1x
444
328
0.76
1.30
1.94
0.04
0.1957
0.0021
1.96
0.04
0.1841
0.0027
+2
2690
25
BR21
-
08G.2
-
4
469
400
0.88
0.45
1.80
0.03
0.1862
0.0015
1.81
0.03
0.1822
0.0019
-
8
2673
17
BR09
-
20J.2
-
1
532
461
0.90
1.18
1.92
0.04
0.1911
0.0013
1.95
0.04
0.1806
0.0020
-
1
2658
18
BR09
-
20L.1
-
1
383
200
0.54
1.17
1.79
0.04
0.1903
0.0014
1.81
0.04
0.1799
0.0022
-
9
2652
20
BR21
-
08H.1
-
1
329
194
0.61
0.47
2.11
0.04
0.1815
0.0029
2.12
0.04
0.1773
0.0033
+6
2628
31
Young outliers
2108I.2
-
1
490
352
0.74
1.27
1.90
0.06
0.1877
0.0016
1.93
0.06
0.1764
0.0029
-
3
2619
27
2108F.1
-
2
671
1495
2.30
0.43
2.04
0.03
0.1784
0.0028
2.05
0.03
0.1746
0.0030
+2
2602
29
9
2108I.1
-
1r
426
261
0.63
0.87
2.20
0.04
0.1817
0.0017
2.22
0.04
0.1739
0.0025
+9
2596
24
2108J.2
-
2
573
368
0.66
0.26
2.01
0.03
0.1743
0.0020
2.01
0.03
0.1720
0.0021
-
1
2577
20
High common
-
Pb and/or discordant data
BR21
-
08F.1
-
1
444
989
2.30
1.29
1.75
0.04
0.1876
0.0016
1.77
0.04
0.1761
0.0028
-
13
2616
26
BR21
-
08G.1
-
1
418
284
0.70
1.48
1.97
0.04
0.1901
0.0017
2.00
0.04
0.1769
0.0030
+0
2624
28
BR21
-
08I.1
-
1
6377
7659
1.24
13.62
2.60
0.06
0.2201
0.0032
3.01
0.08
0.1021
0.0080
-
13
1662
144
BR21
-
08J.1
-
1
4205
5090
1.25
14.44
1.36
0.08
0.2250
0.0057
1.58
0.09
0.1001
0.0121
-
120
1626
225
BR21
-
08J.2
-
1
408
238
0.60
1.56
2.05
0.04
0.1800
0.0016
2.09
0.04
0.1661
0.0028
-
0
2519
28
BR21
-
08K.1
-
1
694
541
0.80
0.74
2.48
0.04
0.1628
0.0012
2.50
0.04
0.1562
0.0017
+12
2415
19
BR21
-
08K.2
-
1
787
853
1.12
1.97
2.28
0.03
0.1913
0.0015
2.32
0.04
0.1737
0.0027
+13
2594
26
BR21
-
08K.3
-
1
476
389
0.84
1.66
1.83
0.03
0.1927
0.0016
1.87
0.03
0.1779
0.0028
-
6
2633
26
BR21
-
08K.3
-
2
635
1145
1.86
0.23
2.60
0.04
0.1602
0.0012
2.61
0.04
0.1581
0.0014
+16
2435
15
BR09
-
20L.2
-
1
543
431
0.82
1.48
1.96
0.04
0.1915
0.0013
1.99
0.04
0.1784
0.0023
+1
2638
21
BR09
-
20L.2
-
2
494
531
1.11
0.65
2.21
0.06
0.1819
0.0013
2.22
0.06
0.1761
0.0018
+10
2617
17
Note:
f
206
is the proportion of common Pb in
206
Pb, determined using the measured
204
Pb/
206
Pb and a common Pb composition from the Stacey
-Kramers (1975) model at the
approximate age of the sample.
Pb
*
represents radiogenic Pb after common Pb correction.
Disc. is apparent discordance, as 100×(t[
207
Pb/
206
Pb]
- t[
206
Pb/
238
U]) / t[
207
Pb/
206
Pb].
The 1
σ
uncertainties include all components of statistical precision.
Analyses are listed in descending order of
207
Pb/
206
Pb, except for the disregarded subgroup.
Data for mount BR09-
20 are from (9).
10
Table S
2.
Input parameters for the Phanerozoic carbon burial model, based on studies of modern
sedimentary basins (model predictions presented in Figure 2
A).
Model input
Supporting references
Delivery flux of organic carbon to
the sediment surface
20 gC m
-2
yr
-1
(2, 3, 10, 11)
, see global flux
calculations in Table S
3.
O
2
penetration depth
1-40 mm
(12)
First
-order rate constant for
aerobic decomposition of TOC
5×10
-5
day
-1
(11, 12)
Anoxic sediment zone burial
efficiency
50%
(1, 8)
Sedimentary rock density
2.7 gr cm
-3
11
Table S
3.
Estimated global fluxes of organic carbon (OC), calculated as areal delivery flux to the
seafloor. The value we used for the Phanerozoic model input (20 gC m
-2
yr
-1
, Table S
2) was
similar to modern global estimates (28.6 gC m
-2
yr
-1
, Table S
3).
Total seafloor
area
(km
2
)
Total seafloor OC
burial flux
(PgC yr
-1
)
Total seafloor
Burial Efficiency
(%)
Areal OC
delivery flux
(gC m
-2
yr
-1
)
Estimate
3.62×10
8
0.155
1.5
28.6
Reference
(13)
(13)
Calculated
12
Table S
4.
Input parameters for the carbon burial model applied to fit the Archean data (model predictions presented in Figures
2B and 2C
).
Scenario
OC delivery flux
(gC m
-2
yr
-1
)
O
2
penetration
depth
(mm)
Anoxic
sediment zone
burial efficiency
(%)
Rate constant for
aerobic decomposition
of TOC
(day
-1
)
Sedimentary
rock density
(gr cm
-3
)
Range
Best fit
Enhanced primary
productivity
(Fig. 2B and 3A)
20-
10,000
10,000
1
50%
5×10
-5
2.7
Anaerobic
model
(Fig. 2C
, 3A
, and 3D
)
0.1-
1
0.33
0
50%
5×10
-5
2.7
Anaerobic model
, higher
anoxic burial efficiency
0.03-
0.3*
0.1*
0
90%
5×10
-5
2.7
*
OC delivery flux required for predicting an identical TOC
-sedimentation rate range as presented in Fig.
2C
, when using the modified
model
(higher anoxic burial efficiency)
.
13
Table S
5.
Net burial efficiency (
[TOC rock
]/[TOC input
]) predicted by the carbon burial model for
the Phanerozoic model and the different Archean scenarios, for a range of sedimentation rates.
For this test, the O
2
penetration depth for the Phanerozoic and enhanced primary productivity
models was set to 1 mm, and the OC delivery flux was set to 20 and 10,000 gC m
-2
yr
-1
,
respectively. In the anaerobic models, the net
burial efficiency is
unaffected by changes in OC
delivery flux. The TOC persistence
component of the model was included in this exercise.
Net burial efficiency
(%)
Sedimentation
rate
(m Ma
-1
)
10
-0.5
10
0
10
0.5
10
1
10
1.5
10
2
10
2.5
Phanerozoic
(Fig. 2A)
0.004%
0.01%
0.2%
8%
28%
42%
47%
Enhanced
primary
productivity
(Fig. 2B and
3A)
0.0%
0.0%
0.1%
0.3%
0.9%
2.7%
9%
Anaerobic
model
(Fig. 2C
,
3A
, and 3D
)
50%
50%
50%
50%
50%
50%
50%
Anaerobic
model,
higher
anoxic burial
efficiency
90%
90%
90%
90%
90%
90%
90%
14
Table S
6.
Net remineralization fluxes predicted by the carbon burial model for the different
scenarios. For this test, the O
2
penetration depth for the Phanerozoic and enhanced primary
productivity models was set to 1 mm, and the OC delivery flux was set to 20 and 10,000 gC m
-2
yr
-1
, respectively. For the anaerobic 50% and 90% burial efficiency models, the OC delivery flux
was 0.33 and 0.1 gC m
-2
yr
-1
, respectively, following the best fit to the Archean data. The TOC
persistence
component of the model was included in this exercise.
Net remineralization flux
(gC m
-2
yr
-1
)
Sedimentation
rate
(m Ma
-1
)
10
-0.5
10
0
10
0.5
10
1
10
1.5
10
2
10
2.5
Phanerozoic
(Fig. 2A)
20.00
20.00
19.97
18.39
14.38
11.67
10.56
Enhanced
primary
productivity
(Fig. 2B and
3A)
10000
10000
9991
9973
9915
9730
9146
Anaerobic
model (Fig. 2C
,
3A
, and 3D
)
0.165
0.165
0.165
0.165
0.165
0.165
0.165
Anaerobic
model,
higher
anoxic burial
efficiency
0.01
0.01
0.01
0.01
0.01
0.01
0.01