differentiated megascopic fossils from the early ediacaran · specimens in upper part of the...
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1. Depositional Environment
The fossiliferous Lantian Member II is interpreted to have deposited in open marine
slope-basinal facies. This interpretation is supported by several lines of evidence.
First, regional mapping shows that the Yangtze Block is a ESE facing passive
continental margin during the early Ediacaran Period, with sandstone-dominated facies to the
west giving way to shale-dominated facies to the east1 (Fig. 1). These two facies are separated
by a transitional siltstone facies and carbonate shoals. The Lantian locality sits in the shale
facies (Fig. 1) that is widely and continuously distributed on the Yangtze Block1. This facies
continuity suggests that the Lantian black shales were not deposited in an isolated lake2 or
restricted lagoon3.
Second, the lack of wave- or current-influenced sedimentary structures suggests that
Lantian Member II black shales were deposited below the wave base. The shales are finely
laminated (Supplementary Fig. 1a) and show no evidence of grading (Supplementary Fig. 1b),
suggesting that they were deposits from suspension settling rather than distal turbidites.
Further, transportation of soft-bodied macrofossils within turbidity current would result in
fossil preservation within beds rather than between beds (or on bedding surface), because the
fossils would be entrained within turbidity currents. However, the Lantian fossils are mostly
preserved on the bedding surface, inconsistent with transportation by turbidity current.
Additionally, transportation within turbidity current would typically result in folding and
deformation of soft-bodied fossils, which are not common among the Lantian fossils.
Third, the lower Lantian Formation contains no sandstone or carbonate interbeds that
would indicate shallow-water facies. It is dominated by organic- and pyrite-rich black shales
that typically weather to buff colors (Supplementary Fig. 1a) because of the oxidation of
pyrite.
The in-situ preservation of epibenthic macroalgae in the Lantian Formation suggests
deposition within the photic zone. Thus, the lower Lantian Formation was not deposited in
abyssal environment like the Conception Group in Newfoundland. Still, the weight of
sedimentary and regional geological evidence suggests that it was deposited in a quiet marine
environment below the wave base. This is consistent with the random orientation of
exceptionally preserved and minimally fragmented macrofossils in the lower Lantian
Formation (Supplementary Fig. 2). The random orientation of benthic marcoalgae also
indicates that deposition of the lower Lantian Formation was not influenced by deep-water
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processes such as turbidity current or contour current, which would have resulted in unimodal
or bimodal orientation of tethered macrofossils, as is the case in the Mistaken Point fossils in
Newfoundland4,5.
Supplementary Figure 1. (a) Field photograph of weathered black shales at excavation site near Lantian in
southern Anhui Province. Rock hammer (30 cm long) for scale. (b) Plane light photomicrograph of fossiliferous
black shale in lower Lantian Formation. Note the lack of graded beds. Dark layers are organic- and pyrite-rich.
Stratigraphic up direction on top.
Supplementary Figure 2. Slab showing multiple specimens with random orientations. Note that the two
specimens in upper part of the photograph are oriented in opposite directions. Scale bar 10 mm.
2. Stratigraphic Correlation and Age Constraints
We estimate that the fossiliferous lower Lantian Formation is of early Ediacaran age,
somewhere between 635 Ma and 576 Ma. Our estimate is based on a robust correlation with
the Doushantuo Formation in the Yangtze Gorges area, which is constrained by several
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radiometric ages.
The correlation between the lower Lantian Formation and the lower Doushantuo
Formation is supported by regional mapping, lithostratigraphy, and chemostratigraphy. The
lithostratigraphic sequence of the Lantian Formation (in southern Anhui) and Doushantuo
Formation (in the Yangtze Gorges area) is similar, including three depositional sequences.
The first sequence consists of a cap dolostone (Member I) followed by a shale-rich member
(Member II). The second depositional sequence is a carbonate rich member (approximately
equivalent to Member III: a dolostone unit overlain by a ribbon rock unit, Supplementary Fig.
3). The third depositional sequence is represented by another black shale unit (Member IV)
and the lower part of the Dengying Formation. As discussed above, black shales of early
Ediacaran age (Member II) can be traced throughout much of the Yangtze Block. In the
Yangtze Gorges area, which was situated in the inner platform in early Ediacaran Period, the
lower Doushantuo Formation contains some argillaceous dolostone beds, but black shale
represents the dominant facies.
The lithostratigraphic correlation between the lower Lantian Formation and lower
Doushantuo Formation is further supported by δ13C chemostratigraphic data. Despite the
abundance of shale, the Lantian Formation does contain two carbonate units. The basal
Lantian cap dolostone has sedimentary features (e.g., sheet cracks) and δ13C values (around
–5‰)6,7 similar to the 635 Ma basal Doushantuo cap dolostone (with the negative δ13C
excursion EN1)8,9. The upper Lantian carbonate (Member III) is characterized with a strongly
negative δ13C excursion7 that is remarkably similar to the negative δ13C excursion EN3 in the
upper Doushantuo Formation (Member III) of the Yangtze Gorges area8; importantly, both
excursions occur in similar facies (thick-bedded dolostone overlain by ribbon rock;
Supplementary Fig. 3).
In the Yangtze Gorges area, a zircon U-Pb TIMS age of 635.2±0.6 Ma is reported from
within the cap dolostone (Member I)10, a zircon U-Pb TIMS age of 632.5±0.5 Ma from the
lower Member II black shale10, a Re-Os age of 593±17 Ma from the lower Member IV black
shale11, and a zircon U-Pb TIMS age of 551.1±0.7 Ma from the uppermost Member IV10. In
addition, Kendall et al. reported a Re-Os age of 598±16 Ma from Doushantuo Member IV
black shale in the Yangtze Gorges area12, which is consistent with the 593±17 Ma Re-Os
age11, although Kendall et al. cautioned the interpretation of the Re-Os ages because of
possible heterogeneity of the black shale samples12. Considering their analytical uncertainty,
these radiometric dates constrain the minimum age range of Member IV between 576 Ma and
550.4 Ma. Thus, the maximum age range of Member II is between 635.8 Ma and 576 Ma. In
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other words, Doushantuo Member II (and by extension the fossiliferous Lantian Member II)
is likely than 576 Ma.
Additionally, Liu et al.13 reported a zircon U-Pb SHRIMP age of 614±7.6 Ma from an
ash bed in the Doushantuo Formation at the Zhangcunping section (Supplementary Fig. 4),
about 60 km to the NE of the Yangtze Gorges area. This ash bed was collected from a
dolostone unit that overlies the lower Doushantuo black shale but underlies an exposure
surface representing a mid-Doushantuo sequence boundary. A traditional correlation14 using
the mid-Doushantuo sequence boundary, biostratigraphic data, and δ13C chemostratigraphic
data would correlate this ash bed to a horizon within the upper part of Doushantuo Member II
in the Yangtze Gorges. Adopting this correlation, the 614±7.6 Ma age gives a direct age
constraint on Doushantuo Member II and Lantian Member II. Similarly, a Pb-Pb age of
599±4 Ma15 has been reported from the upper Doushantuo phosphorite at Weng’an, above the
mid-Doushantuo exposure surface (Supplementary Fig. 4). Again, adopting the traditional
correlation between upper Doushantuo phosphorite/dolostone at Weng’an and Doushantuo
Member III/IV in the Yangtze Gorges8, the 599±4 Ma age provides a minimum age constraint
on Doushantuo Member II. Together, these two ages constrain the mid-Doushantuo sequence
boundary between 614±7.6 Ma and 599±4 Ma, and provide further support for a 576 Ma
minimum age of Doushantuo Member II which lies below the sequence boundary.
An alternative correlation has been proposed that the upper Doushantuo dolostone
above the mid-Doushantuo exposure surface at Zhangcunping and Weng’an be correlated
with the lower Doushantuo Member II in the Yangtze Gorges area16. This alternative
correlation was motivated by the presumed correlation of EN2 and the associated
mid-Doushantuo flooding surface or sequence boundary (see Supplementary Fig. 4) with the
582 Ma Gaskiers glaciation10,16. Not only is this alternative correlation inconsistent with
lithostratigraphy and sequence stratigraphy, it is also in disagreement with available
biostratigraphic data: the lower Doushantuo Member II in the Yangtze Gorges hosts an
acritarch assemblage that is distinct from acritarchs from the upper Doushantuo dolostone at
Zhangcunping and upper Doushantuo phosphorite/dolostone at Weng’an13,14,17. Finally, this
alternative correlation is inconsistent with chemostratigraphic data (Fig. 1; Supplementary
Fig. 4) which show the presence of EP2 in the upper Doushantuo dolostone at Zhangcunping,
Weng’an, and Yangtze Gorges area8. We would like to emphasize that the minimum age of
576 Ma for the Lantian biota is derived from the correlation between Lantian and Yangtze
Gorges areas; it is corroborated by, but not dependent on, the validity of the traditional
correlation between Weng’an, Zhangcunping, and Yangtze Gorges areas. Taken at face value,
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a minimum age of 576 Ma still allows a marginal temporal overlap between the Lantian biota
and the 579–565 Ma Avalon biota18-20. However, fossiliferous Lantian Member II is separated
from Lantian Member IV (= Doushantuo Member IV, from which the 593±17 Ma age came)
by a complete depositional sequence, and the fossiliferous horizon is ~20 m below Lantian
Member III. Thus, we consider the Lantian biota is likely older than the Avalon biota18-20.
Beyond South China, the correlation becomes more tenuous, particularly the correlation
with the exceptionally dated 582 Ma Gaskiers glaciation in Newfoundland21. It is widely
accepted that EN3 in the Yangtze Gorges area is correlated with the Shuram negative δ13C
excursion22-26, but the temporal relationship between the Shuram and the Gaskiers is
controversial. Condon et al.10 and Sawaki et al.16, partly driven by the assumption that the
Shuram event could not have lasted >10 myr, correlated the mid-Doushantuo sequence
boundary and the associated δ13C feature EN2 (=Shuram) with the Gaskiers glaciation.
However, this correlation is in direct conflict with the 599±4 Ma Pb-Pb age from Weng’an
and the 593±17 Ma Re-Os age from the Yangtze Gorges, both from levels above EN2 and
above the mid-Doushantuo flooding surface15. Thus, we accept the alternative correlation that
EN3 (or Shuram) started 580-600 Ma22-26 and may have lasted more than 10 myr.
Supplementary Figure 3. Ribbon rocks (limestone and dolostone intercalations) in the upper Doushantuo
Formation in the Yangtze Gorges area (a) and the upper Lantian Formation in southern Anhui (b). Both are
characterized by strongly negative δ13C values down to –10‰. Limestone is light grey in color, whereas
dolostone is dark grey [buff color in (a) due to weathering]. Coin in (a) is 21 mm in diameter.
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Supplementary Figure 4. Locality maps and stratigraphic columns, with biostratigraphic, chemostratigraphic, and geochronological data. (a) Yangtze Block (YB) in relation
to North China Block (NCB) and Tarim Block (TB). (b) Early Ediacaran facies distribution on Yangtze Block (simplified from Zhu et al.1), showing the localities of Yangtze
Gorges (YG), Lantian (LT), Zhangcunping (ZCP), and Weng’an (WA). (c) Lantian section. Carbonate δ13C data for basal Lantian cap dolostone (EN1) from Zhou et al.6, and
those for upper Lantian Formation from this study (Supplementary Table 1). (d) Jiulongwan (Yangtze Gorges) section. δ13C and radiometric dates from previously published
data10,11,27,28. Stratigraphic thickness scale bar applies to the Doushantuo Formation only. DY, Dengying Formation. (e) Weng’an section. δ13C and radiometric dates from
previously published data15,17,29. Cryo: Cryogenian. (f) Zhangcunping section. Radiometric date from Liu et al.13. δ13C data from this study (Supplementary Table 2). The two
acritarch biozones are recognized by McFadden et al.14.
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3. Estimate of Taxonomic Diversity Yan et al.30 described 11 taxa of macroscopic carbonaceous compression fossils from
the lower Lantian Formation. Later, Chen et al.31 reported 13 additional species from the same horizon. Yuan et al.3 carried out a systematic revision of the Lantian fossils. After synonymizing some taxa described by Yan et al.30 and Chen et al.31, Yuan et al.3 estimated that there are 12 forms of macroscopic algal fossils in the Lantian biota, including 10 named taxa and 2 unnamed forms.
Our new excavation revealed at least 6 new forms, bringing the total number of morphotaxa to be 18. We realize that the taxonomy of the Lantian fossils is complicated by ontogenetic and preservational issues. For example, as mentioned in the main text, there may be possible ontogenetic relationship between Type A, Type B, and Flabellophyton despite the lack of transitional forms. Also, the same taxon may appear very different depending on how it is compressed, a complication that has been long appreciated by paleontologists working on the Burgess Shale and Chengjiang biotas32,33. Indeed, a case may be made that some specimens described as Anhuiphyton lineatum in Yuan et al.3 could represent a species of Flabellophyton compressed top-down (as opposed to sideway or lateral compression typically seen in Flabellophyton species). Realizing these ontogenetic and preservational issues, we estimate that there are ~15 distinct morphotaxa in the Lantian biota.
4. δ13C and δ18O Data
δ13C and δ18O analysis followed standard procedures described in the literature34.
Fresh carbonate samples were cut into chips. Carbonate powders were made from fresh chips
for isotope analysis. CO2 was extracted using standard offline technique, with powder
reacting with concentrated H3PO4 at 25°C for 12 h. Isotope ratios were measured using a
Finnigan MAT 253 mass spectrometer at Nanjing Institute of Geology and Palaeontology,
Chinese Academy of Sciences. δ13C and δ18O are reported as ‰ deviation from VPDB.
Analytical precision is better than 0.1‰ for δ13C and 0.3‰ for δ18O. No effort was made to
distinguish dolomite and calcite mineral facies as Zhao and Zheng did7. δ18O values were not
corrected for dolomite.
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Supplementary Table 1. Carbonate δ13C and δ18O values (‰, VPDB) of the Lantian Formation near Lantian
Village in southern Anhui Province. Note that stratigraphic height measurements use a datum at the base of the
third member of the upper Lantian Formation, rather than the base of the Lantian Formation. Zhao and Zheng7
reported similar δ13C data (around –10‰) from equivalent strata at a nearby section, but their δ18O values
(around –20‰) are much lower. They interpreted the extremely low δ18O values as evidence for isotope
exchange with glacial meltwater. Alternatively, such low δ18O values could indicate diagenetic alteration.
Regardless, the similar δ13C values between the two measured sections suggest that the δ13C values were
buffered against isotopic re-equilibration despite oxygen isotope exchange.
sample # lithology Height (m) δ13CVPDB δ18OVPDB 10LJL-01 limestone 27.4 -10.9 -14.1 10LJL-02 limestone 25.9 -11.2 -14.3 10LJL-03 dolostone 24.4 -8.9 -9.9 10LJL-04 dolostone 24.0 -8.8 -9.8 10LJL-05 dolostone 23.5 -9.0 -6.6 10LJL-06 dolostone 23.1 -9.3 -7.2 10LJL-07 dolostone 22.8 -9.9 -7.4 10LJL-09 limestone 17.8 -11.9 -14.6 10LJL-11 limestone 9.8 -9.4 -14.8 10LJL-12 limestone 8.8 -9.1 -15.2 10LJL-13 dolostone 7.8 -8.1 -8.4 10LJL-14 dolostone 6.3 -7.0 -9.8 10LJL-15 limestone 4.8 -9.7 -13.2 10LJL-15A dolostone 4.6 -0.7 -6.7 10LJL-16 dolostone 4.4 -1.0 -7.5 10LJL-17 dolostone 4.1 -2.8 -10.5 10LJL-18 dolostone 3.8 -1.9 -9.3 10LJL-19 dolostone 3.4 -2.2 -10.3 10LJL-20 dolostone 1.4 0.0 -6.2 10LJL-21 limestone 1.0 -5.6 -14.3 10LJL-22 dolostone 0.5 -2.2 -10.5 10LJL-23 dolostone 0.0 -7.5 -14.6
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Supplementary Table 2. Carbonate δ13C and δ18O values (‰, VPDB) of the Doushantuo and lower Dengying Formations at the Zhangcunping section, Hubei Province. Contact between the Doushantuo Formation and the underlying Nantuo Formation is not well exposed. Stratigraphic height measurements were made using a datum at the base of the exposed Nantuo Formation.
sample # Height (m) δ13CVPDB δ18OVPDB
05WJG-07 3.0 -2.0 -6.4 05WJG-06 3.3 -1.5 -6.5 05WJG-05 3.6 -0.6 -5.5 05WJG-04 3.9 -0.4 -5.9 05WJG-03 4.2 -0.2 -5.8 05WJG-02 4.5 -0.2 -5.8 05WJG-01 4.8 -1.3 -6.3 05WJG-08 24.0 0.9 -5.2 05WJG-09 24.3 2.4 -5.9 05WJG-10 24.7 2.2 -5.1 05WJG-12 25.3 2.8 -5.4 05WJG-13 25.6 2.8 -5.4 05WJG-14 25.9 3.4 -6.1 05WJG-15 26.2 3.2 -5.6 05WJG-16 26.5 2.9 -6.3 05WJG-17 26.8 3.0 -6.0 05WJG-18 27.1 3.5 -5.6 05WJG-19 27.4 3.7 -6.3 05WJG-20 27.7 2.6 -5.9 05WJG-21 28.0 2.7 -5.4 05WJG-22 28.3 2.8 -6.0 05WJG-23 28.6 3.2 -6.3 05WJG-24 30.0 3.1 -5.4 05WJG-25 30.3 2.2 -7.2 05WJG-26 30.6 3.4 -5.6 05WJG-27 30.9 2.9 -6.1 05WJG-28 31.2 2.3 -6.4 05WJG-29 31.5 1.2 -6.7 05WJG-30 31.8 1.8 -6.6 05WJG-31 32.1 0.2 -7.9 05WJG-32 32.4 1.5 -7.1 05WJG-33 32.7 2.4 -6.0 05WJG-34 33.0 2.4 -5.7 05WJG-45 34.3 0.6 -3.8 ZCP-32 36.0 -0.4 -4.6 ZCP-33 36.3 -1.6 -4.3 ZCP-34 36.5 0.9 -4.6
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ZCP-36 38.0 1.6 -4.0 ZCP-39 44.0 4.7 -5.3 ZCP-40 49.0 4.9 -4.6 ZCP-41 59.0 3.8 -4.6 ZCP-43 60.0 4.4 -4.1 ZCP-44 61.0 5.1 -4.6
ZCP-45 62.0 3.4 -3.9 ZCP-46 67.0 2.4 -4.0 ZCP-47 70.0 5.6 -4.0 ZCP-48 71.0 4.8 -4.3 ZCP-49 74.0 -1.3 -1.9 ZCP-51 84.0 4.3 -4.1 ZCP-52 85.0 3.4 -4.0 ZCP-53 86.0 3.7 -3.0 ZCP-54 86.5 3.2 -2.6 ZCP-55 86.6 3.1 -1.6 ZCP-56 87.6 2.7 -1.7 ZCP-57 89.6 3.4 -0.5
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