1
2
3
Supplemental Materials: Impact of Dissolution, Bioturbation and Winnowing on the
Sedimentary Record of the Paleocene-Eocene Thermal Maximum
4
1. Quantifying dissolution during the PETM
5
In Supplemental Figure 1 we plot percent dissolution versus paleodepth for all PETM sites
6
with available CaCO3 data as compiled by Panchuk (2007), with the addition of the new data
7
from Site 690 and data from Site 401 from Cecily Palike (pers. comm., 2013) (Table 1). We
8
exclude Site 865 from the plot as the PETM section is clearly incomplete (e.g., Bralower et
9
al., 1995).
These data suggest that Shatsky Rise Sites 1209-1212 were apparently
10
characterized by less intense dissolution than other sites at comparable paleodepths with the
11
exception of Sites 690 and 401 (N. Atlantic). We propose that the impact of dissolution on
12
carbonate at Site 1209 has been diminished by bioturbation as discussed in Section 4.2.
13
However, changes in the fluxes of carbonate may also have played a role.
14
15
Supplemental Materials Figure 1. Percent dissolution determined using the technique of
16
Broecker (1995). Red numbers are Pacific Sites, blue are sites in the Atlantic, Caribbean and
17
Southern Ocean. See Table 1 for data.
18
19
20
21
22
23
24
25
26
Site
Latitude
Depth (m)
CaCO3
high
CaCO3
low
Percent
Dissolution
%
Pacific
1209
1210
1211
1212
865
1220
1221
22.00
21.75
21.6
21.9
5.46
-3.08
-5
1900
2100
2400
2200
1500
2900
3200
96
92
95
98
96
90
74
84
86
78
83
93
0
3
0.84
0.86
0.78
0.83
0.93
0
0.03
78.1
46.6
81.3
90.0
44.6
100.0
98.9
Caribbean
999
1001
7.5
11
1750
1500
61
45
0
0
0
0
100.0
100.0
North
Atlantic
401
527
549
1051
42.28
-35
43.79
28.90
1900
2400
2150
1500
56.65
83
51
56
27.89
0
1
52
0.28
0
0.01
0.52
70.2
100.0
99.0
14.9
South
Atlantic
1262
1263
1266
1267
-34.8
-36
-36
-36.2
3600
1500
2600
3200
88
88
85
80
1
1
4
1
0.01
0.01
0.04
0.01
99.9
99.9
99.3
99.7
27
Southern
Ocean
690
-65.4
1950
85
60
0.6
73.5
738
-61.98
1350
90
70
0.7
74.1
Table 1. Dissolution percent calculated from pre (high) and peak (low) CaCO3 contents after
28
Broecker (1995).
29
30
Sites 690, 1209 and 1262 and all PETM sections are characterized by predominantly
31
biogenic sediment sources (largely nannoplankton and planktic foraminifera) with minor
32
contributions from aeolian and clastic sources. In all likelihood, fluxes of carbonate and non-
33
carbonate particles changed during the PETM with variation in plankton production,
34
weathering and aeolian transport (e.g., Robert and Kennett, 1994; Ravizza et al., 2001;
35
Bralower, 2002; Kelly, 2002; Gibbs et al., 2006; Petrizzo, 2007). However, there is no way to
36
determine exactly the changes in these fluxes, nor can we estimate the loss of highly fragile
37
plankton species that are only preserved in clay-rich, hemi-pelagic deposits along continental
38
margins (e.g., Bown et al., 2008). The dissolution estimates (Figure 6 and Supplemental
39
Figure 1) are based on assuming that the fluxes from the different sources remained constant.
40
41
At the three study sites the amount of dissolution estimated from the change in percent
42
CaCO3 (Broecker, 1995, 2009; Stap et al., 2009; Stap, 2010) at the peak of the PETM is over
43
60%, over 70%, and 100% of the carbonate at Sites 690, 1209, and 1262, respectively
44
(Figures 6a,b). At Site 1262, complete dissolution is clear from the absence of CaCO3 in the
45
interval corresponding to the peak of the PETM. At Site 690, impoverished nannofossil
46
preservation supports the notion of a significant amount of dissolution, quite possibly
47
approaching 60%. However, nannofossil preservation at Site 1209 does not reveal
48
dissolution to the extent of 70% of the sediment (Plate 1). As discussed bioturbation has
49
likely masked the extent of dissolution at this site. In addition, the assumption of constant
50
production of carbonate has led to an overestimate of the calculated levels of dissolution at
51
Sites 690 and 1209.
52
53
Plankton assemblages suggest oligotrophic conditions in open-ocean locations during the
54
PETM (Bralower, 2002; Gibbs et al., 2006), and carbonate production rates at these sites are
55
likely to have decreased modestly during the initial stages of the PETM (e.g., Kelly et al.,
56
2012). Gibbs et al. (2010) estimated a carbonate production rate decrease of ~15-20% at Site
57
690 and ~5% at Site 1209.
58
pump was less efficient at Site 690 than at Site 1209 where the water column was stratified in
59
the early part of the PETM (Schneider et al., 2013). Thus the decrease in carbonate supply
60
might have been more significant at Site 1209. At Site 690, clay accumulation may have
61
accelerated as a result of enhanced continental weathering on the nearby Antarctic continent
62
(Robert and Kennett, 1994).
63
64
However, GENIE model simulations suggest that the biological
65
2. Products of Dissolution
66
When sediment is chemically eroded, a significant amount of the dissolved carbonate is
67
released into pore waters. At Site 1209, the dissolved carbonate appears to have
68
reprecipitated as long 5-15 µm calcite blades (Colosimo et al., 2006) (Supplemental Plate 1).
69
Large blocks of reprecipitated carbonate hosting whole foraminiferal shells and molds of
70
foraminifera have been observed at Site 865, another site where the brevity of the PETM
71
interval is likely partially a result of burndown (Supplemental Plate 1, see similar objects in
72
Kozdon et al., 2013). At Site 1262, small rhombs of dolomite or calcite are observed in
73
samples with low or no carbonate; these rhombs are possibly precipitates of dissolved
74
carbonate. At Site 690 it is impossible to distinguish between micarb and clay in electron
75
micrographs, but at >50% CaCO3, some of the significant volume of fine grained material
76
(Plate 1) must be micarb derived from reprecipitation of the dissolved CaCO3.
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
Supplemental Materials Plate 1. Electron micrographs showing nannofossil preservation
across the base of the CIE at Site 690. The micrographs can distinguish the abundance
and preservation of coccolith carbonate, but cannot generally distinguish between clay
and micarb. a. 170.53-170.65 mbsf; b. 170.67-170.73 mbsf; c.170.74-170.79 mbsf; d.
170.80-170.82 mbsf. Samples below 170.80 show moderate dissolution with samples
dominated by coccoliths and pieces of coccoliths and a lower volume of clay/micarb.
Between 170.80 and 170.75 mbsf there is a substantial decline in preservation with fewer
coccoliths with more etched rims and more clay/micarb. Samples are poorly preserved
up to 170.70 mbsf. Coccolith preservation is very poor from 170.69 to 170.65 mbsf with
few whole coccoliths and a lot of clay/micarb. Samples from 170.64 mbsf and above
have an increasing number of whole coccoliths with a lower volume of clay/micarb.
Onset of the bulk CIE is at 170.70 mbsf (Figure 2).
Supplemental Materials Plate 2. Electron micrographs showing nannofossil preservation
across the base and lower part of the CIE at Site 1209 (Section 22H-1). a. 196.47-196.51
mbsf; b. 196.46-196.44 mbsf; c. 196.28 and 196.42 mbsf. Samples are dominated by
nannofossils. For most of the section, fossil preservation is moderate. There is a slight
decline in preservation between 196.46 and 196.47 mbsf. Lithologic boundary and CIE
are at 196.45 mbsf (Figure 3).
Supplemental Materials Plate 3. Morphology of calcite likely derived from reprecipitation of
calcite dissolved in the PETM. a. and b. Calcite blades on planktonic foraminifera from
Site 1209. c. and d. Blocks of reprecipitated calcite hosting foraminifera from Site 865.
Scale bars in c. and d. are 100 µm.
105
106
107
3. Interpreting bioturbation and winnowing from single specimen and bulk records
108
In Section 4.3 we discuss evidence for bioturbation and winnowing, including single
109
specimen foraminiferal and bulk stable isotopes. In Supplemental Materials Figure 2a we
110
show single specimen planktonic isotope and bulk isotope records from Site 690 (data
111
from Thomas et al., 2002). As discussed in the text, the single specimen data show 10
112
specimens that are clearly out of place, two specimens of Subbotina that have been mixed
113
upwards and eight specimens of Acarinina that have been mixed downward. Any of
114
these specimens could be the result of bioturbation and winnowing. Bioturbation is most
115
likely to mix foraminiferal specimens downward while winnowing has the potential to
116
mix specimens upwards, thus the Subbotina specimens are more likely mixed via
117
winnowing and the specimens of Acarinina mixed via bioturbation. It is unlikely that
118
bioturbation has transported these specimens by 20 cm. This mixing is more likely the
119
result of downhole contamination during drilling.
120
121
122
123
Supplemental Materials Figure 2a. Distribution of single specimen and bulk carbonate
124
carbon isotope values at Site 690 (data from Thomas et al. 2002). All samples are from
125
the archive half of the core. Circles designate samples out of place potentially as a result
126
of bioturbation or winnowing. Lines indicate levels of samples with grain size
127
distributions potentially indicative of winnowing.
128
129
130
131
132
Supplemental Materials Figure 2b. Distribution of single specimen oxygen isotope
133
values at Site 690 (data from Thomas et al. 2002). All samples are from the archive half
134
of the core. Circles designate samples out of place potentially as a result of bioturbation
135
or winnowing. Lines indicate levels of samples with grain size distributions potentially
136
indicative of winnowing.
137
138
Grain size data allow us to identify samples that have distributions potentially altered by
139
winnowing (Supplemental Figure 3). We indicate these samples in Supplemental
140
Materials Figure 2. The lack of coincidence between samples with isotope values that are
141
out of place and those that have grain size distributions consistent with winnowing
142
suggests that winnowing is not the cause of displacement. Possibly, the two specimens of
143
Subbotina have been mixed downwards by drilling.
144
From the single specimen isotope data it is possible that a number of specimens that are
145
not clearly out of place have been mixed by bioturbation and winnowing, just not to the
146
extent that would distinguish them from surrounding specimens. This is particularly the
147
case close to the carbon isotope excursion.
148
149
150
151
152
153
154
155
156
157
158
159
Supplemental Materials Figure 3. Logarithmic grain size profiles for samples from across
the base of the PETM at the three study sites. 10% scale bar is volume abundance of the
sediment fraction. The data show unimodal and relatively homogenous distributions at
Sites 1209 and 1262; both sites show a shift towards finer grain size in samples from the
earliest part of the PETM (196.45-196.42 mbsf at Site 1209; 140.1-139.9 mcd at 1262).
Samples at Site 690 generally show a more bimodal grain size distribution than the other
two sites, with most samples possessing a very minor but still distinguishable peaks likely
representing nannoplankton and foraminifera. Some samples (including 170.36, 170.45,
170.53, 170.69, 170.725, 170.755, 170.845 mbsf) show a more pronounced foraminiferal
peak.
160
161
The impact of bioturbation can clearly be observed in bulk carbonate isotope data from
162
Site 690. We plot bulk carbonate isotopes data from the two halves of Section 19-1 in
163
Supplemental Materials Figure 3. The plot shows largely comparable values between
164
170.4 and 170.8 meters below sea floor with the exception of the interval between 170.62
165
and 170.69 mbsf where a burrow has clearly mixed the bulk carbonate isotope values in
166
the archive half with respect to the working half.
167
168
169
Supplemental Materials Figure 4. Bulk carbonate carbon isotope values of the archive
170
half of the PETM (Section, 690B-19H-1) (from Thomas et al., 2002) plotted against
171
values from the working half (from Bains et al., 1999).
172
173
174
175
Increase in fragmentation
Benthic Foraminiferal Extinction
Carbon isotope excursion (bulk CaCO3)
Decrease in CaCO3
Site 690
mbsf
170.6
170.60-170.61
170.70
170.79
Site 1209
mbsf
196.525
196.45
196.45
196.465
Site 1262
mcd
140.10-140.16
140.18
Above 140.13
140.14
176
Deterioration of nannofossil preservation
Base of claystone
170.75-170.80
NA
196.465
196.45
140.14
140.14
177
Supplemental Materials Table 2. Level of significant changes associated with the PETM
178
at the three study sites (See Figure 2)
179
180
181
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