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Triassic–JurassicclimateincontinentalhighlatitudeAsiawasdominatedbyobliquitypacedvariations(JunggarBasin,Ürümqi,
China)
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Triassic–Jurassic climate in continental high-latitude
Asia was dominated by obliquity-paced variations
(Junggar Basin, Ürümqi, China)
Jingeng Shaa,1, Paul E. Olsenb,1, Yanhong Pana, Daoyi Xuc, Yaqiang Wanga, Xiaolin Zhangd, Xiaogang Yaoa,
and Vivi Vajdae,f
a
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Nanjing 210008, China; bLamont-Doherty Earth
Observatory of Columbia University, Palisades, NY 10968; cInstitute of Geology, China Earthquake Administration, Beijing 100029, China; dChinese Academy
of Sciences Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China,
Heifei 230026, China; eDepartment of Geology, Lund University, 223 62 Lund, Sweden; and fDepartment of Palaeobiology, Swedish Museum of Natural
History, 104 05 Stockholm, Sweden
Empirical constraints on orbital gravitational solutions for the
Solar System can be derived from the Earth’s geological record of
past climates. Lithologically based paleoclimate data from the
thick, coal-bearing, fluvial-lacustrine sequences of the Junggar Basin of Northwestern China (paleolatitude ∼60°) show that climate
variability of the warm and glacier-free high latitudes of the latest
Triassic–Early Jurassic (∼198–202 Ma) Pangea was strongly paced
by obliquity-dominated (∼40 ky) orbital cyclicity, based on an age
model using the 405-ky cycle of eccentricity. In contrast, coeval
low-latitude continental climate was much more strongly paced
by climatic precession, with virtually no hint of obliquity. Although
this previously unknown obliquity dominance at high latitude is
not necessarily unexpected in a high CO2 world, these data deviate
substantially from published orbital solutions in period and amplitude for eccentricity cycles greater than 405 ky, consistent with
chaotic diffusion of the Solar System. In contrast, there are indications that the Earth–Mars orbital resonance was in today’s 2-to-1
ratio of eccentricity to inclination. These empirical data underscore
the need for temporally comprehensive, highly reliable data, as
well as new gravitational solutions fitting those data.
|
orbital forcing obliquity cycle
solar system chaos
| Triassic–Jurassic | lacustrine sediments |
It is a collisional successor basin, established during the Late
Permian, 50–75 My after the cessation of subduction and complex
amalgamation of microplates and ocean basins. Triassic and Early
Jurassic age strata amount to 3,600 m in the interior, subsurface
region of the basin (7) but outcrop extensively in several areas.
One of the largest outcrops is the Haojiagou section located about
50 km southwest of Ürümqi City on the southern margin of the
Junggar Basin of northern Xinjiang Uygur (Uighur) Autonomous
Region, Northwestern China (Fig. 1 and Fig. S1) that forms the
basis for this report. There, the 1,050 m of the nonmarine Haojiagou and coal-bearing Badaowan formations are continuously
exposed and only slightly deformed (Fig. S2). The section has been
studied in various aspects (e.g., see SI Text), but only one summary
on the cyclostratigraphy has been published to date (8).
The paleolatitude of the Junggar Basin for the Triassic–Jurassic
is most parsimoniously placed at about 60° N (Fig. 1), constrained
by paleomagnetic data (9) interpreted in light of the effects of
compaction-induced inclination error (10) and plate-tectonic
context (e.g., ref. 7; see SI Text). It is the highest latitude continental basin in which Triassic–Jurassic orbitally paced cyclicity has
been quantitatively examined.
Significance
O
ur understanding of Triassic and Early Jurassic high-latitude climate, biotic evolution, mass extinction, and geochronology is very poor in contrast to that of the contemporaneous
tropics (1, 2). This poor resolution impairs an elucidation of the
basic patterns of Earth system function during the early Mesozoic,
notably the high-latitude climatic response to orbital forcing, as well
as the effects of the eruption of the Triassic–Jurassic Central
Atlantic Igneous Province (CAMP) (3). The former issue bears on
the stability of the Solar System, in which determining variations in
orbital eccentricity (via climatic precession) and inclination (via
obliquity) figure as crucial (4–6), and the latter bears on the causes,
effects, and recovery from the end-Triassic mass extinction (ETE)
(e.g., ref. 2). Here, we describe results of a cyclostratigraphic investigation of lithologic variations in the paleo-high latitude, lacustrine,
Late Triassic–Early Jurassic Haojiagou and Badaowan formations
of the Junggar Basin, China representing, to our knowledge, the
first analysis of orbital cyclicity from a high-latitude, early Mesozoic
continental sequence, and a step toward development of an empirical basis for evaluating numerical solutions of Solar System
chaotic behavior.
Junggar Basin, Ürümqi, Western China
The thick, nonmarine, early Mesozoic sequence of the Junggar Basin
of Western China (Fig. 1 and Figs. S1 and S2) comprises >11 km
of largely nonmarine Late Paleozoic to Cenozoic strata deposited in the northwestern-most of the “walled basins” of China (7).
www.pnas.org/cgi/doi/10.1073/pnas.1501137112
Geological records of paleoclimate provide the only constraints
on Solar System orbital solutions extending beyond the ∼50-Ma
limit imposed by chaotic diffusion. Examples of such constraints
are coupled high and low latitude, Triassic–Jurassic (∼198–202 Ma)
sedimentary cyclicity in coal-bearing outcrops from the ∼60° Npaleolatitude Junggar Basin (Western China), and contemporaneous tropical basins. Analysis reveals climate variability
dominated by obliquity-scale cyclicity in the Junggar Basin and
precession-scale cyclicity in the tropics. Together, these geological records empirically constrain orbital solutions by providing joint g4 − g3 and s4 − s3 secular frequency estimates of
the Earth–Mars orbital resonance. These results demonstrate
the opportunity for developing a new class of solutions grounded
by geological data extending hundreds of millions of years into
the geologic past.
Author contributions: J.S., P.E.O., and D.X. designed research; J.S., P.E.O., Y.P., Y.W., X.Z.,
X.Y., and V.V. performed research; J.S., P.E.O., D.X., and V.V. analyzed data; P.E.O. wrote
the paper; J.S. was the leader of expeditions to Ürümqi and helped write the paper; Y.P.,
Y.W., X.Z., and X.Y. collected data; and V.V. analyzed samples.
Reviewers: L.A.H., Johns Hopkins University; and M.R.R., New York University.
The authors declare no conflict of interest.
Freely available online through the PNAS open access option.
1
To whom correspondence may be addressed. Email: [email protected] or
[email protected].
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.
1073/pnas.1501137112/-/DCSupplemental.
PNAS Early Edition | 1 of 6
EARTH, ATMOSPHERIC,
AND PLANETARY SCIENCES
Contributed by Paul E. Olsen, January 18, 2015 (sent for review December 19, 2014; reviewed by Linda A. Hinnov and Michael R. Rampino)
In contrast to the present, Late Triassic–Early Jurassic highlatitude regions had warm, humid climates according to the
presence of broad-leaf gymnosperm macrofossil assemblages from
both formations (SI Text) and the presence of coal, consistent with
many early Mesozoic northern hemisphere high-latitude sedimentary basins (11).
The Haojiagou section exposes 350 m of Haojiagou Formation
and 700 m of Badaowan Formation. The lower and upper members have a significant fluvial component with coal beds, and the
middle member consists of largely lacustrine deposits with coal
seams (8) (SI Text). The termination of the end-Triassic extinction
(ETE) interval is placed at the last appearance datum of the
sporomorph Lunatisporites rhaeticus in bed 52 and is used as a tie
point to pin the latest Rhaetian end of the ETE within the studied
successions (Fig. 2, Fig. S3, and SI Text). In eastern North America,
the last appearance of this pollen taxon occurs in strata about 60 ky
younger than the initiation of the initial ETE, constrained by both
U-Pb dates and astrochronology (2, 12), and the Triassic–Jurassic
boundary occurs about 40 ky after that based on extrapolation and
correlation with United Kingdom sections (12).
LITH Index
Cyclicity is visually evident at multiple scales in the Haojiagou
and Badaowan formations in outcrop as alternations of organicrich mudstones with sandstone and conglomerate beds (Fig. S2).
To quantify this cyclicity and examine its possible periodicity in
thickness, we constructed a scale of lithologies based largely on
grain size (Fig. 2, Figs. S3 and S4, and Table S1) termed the LITH
index, which, in a broad way, can be interpreted as a proxy of the
degree of flooding of the land surface during deposition. At low
LITH values, coals and organic-rich black mudstones represent
the most flooded environment (analogous to certain Neogene lake
cycles) (e.g., ref. 13) and high LITH values, predominately conglomerates, the least flooded, with unimpeded fluvial systems
flowing toward the basin depocenter. Many of the organic-poor,
poorly bedded mudstones and sandstones with intermediate LITH
values are pedogenically modified. The fluctuations in LITH index
are thus a proxy for climatic variability in precipitation and evaporation, ultimately driven by insolation changes.
Carroll et al. (7) classify the lacustrine environment for both
the Haojiagou and Badaowan formations as “overfilled” freshwater
Pangea
201 Ma
60
Newark
Basin
Pucara
Basin
CAMP
Junggar
Basin
°
Bristol Channel
Basin
equator
Continental crust
Ocean crust
Fig. 1. Position of the Triassic–Jurassic Junggar Basin at 201 Ma and other
basins discussed in SI Text. CAMP is the Central Atlantic Magmatic Province (3).
2 of 6 | www.pnas.org/cgi/doi/10.1073/pnas.1501137112
lakes, and the lake level variations are typical of “forced regressions” in a sequence stratigraphic framework (14). The upper
Haojiagou Formation is characterized dominantly by largely lake
margin and fluvial environments for the interbedded mudstone,
sandstones, and coal. The muted lake level fluctuations of the
Haojiagou Formation are followed by an increase in the magnitude
of fluctuations in the Badaowan Formation, marked by an increase
in coal thickness and sandstone abundance comprising braided
fluvial systems feeding into the lake. This relationship suggests
increased clastic input to the basin associated with an increase in
humidity and intensification of the hydrological cycle into the
earliest Jurassic, as inferred for other parts of the world for the
Triassic–Jurassic transition (15). Overall the general facies interpretation of the Haojiagou and Badaowan formations is similar
to the Triassic–Jurassic Kap Stewart Formation of Jamesonland,
Greenland, the latter also interpreted in terms of lacustrine forced
regressions compatible with a Milankovitch interpretation of the
thickness periodicities (16).
Thickness Periodicities in the Junggar Basin
We chose four methods of examining the thickness periodicities
of the Haojiagou and Badaowan formations (see Methods and SI
Text): (i) multitaper method (MTM) spectral estimates that include an f-test for significance (Fig. 3 and Figs. S4 and S5);
(ii) evolutive wavelet spectra (Fig. 4); (iii) simple periodograms
[fast Fourier transforms (FFTs)] (Fig. S4); and (iv) Blackman–
Tukey spectra with cross-spectral coherence (Fig. S5). The LITH
index has significant variance symmetrical around the mean, and,
because all three of these methods are insensitive to such variance, the LITH data were clipped at a value of 60, with the lower
values being used for this analysis (the high values give the same
results—see SI Text and Fig. S5). Because of the lack of temporal
constraints on the middle and upper Badaowan Formation and
its less obvious periodicities, we focused on the lower Badaowan
and upper Haojiagou formations.
Using these methods, a periodic signal was most clearly apparent between 450 m and 950 m in the upper Haojiagou and
lower Badaowan formations, with a prominent continuously fluctuating thickness period of between 20 m and 40 m (Figs. 3 and 4
and Figs. S4 and S5). Periodicities were revealed in more detail by
the FFT and MTM analyses (Fig. 4 and Figs. S4 and S5), with the
strongest and most significant thickness periodicities at around
3–6 m and 20–40 m (Figs. 3 and 4 and Figs. S4 and S5) although
other important periodicities are present and discussed below.
Eccentricity and Obliquity Cyclicity in the Junggar Basin
The biostratigraphic constraints (see SI Text and Fig. S3) on the
Badaowan Formation suggest that the lower to middle Badaowan should span the entire Hettangian age and part of the Sinemurian. Because the duration of the Hettangian Age is about
2.0 ± 0.1 My (12, 17–19), the 300-m-thick lower to middle
Badaowan should span ∼2–4 My. Given these constraints, the 20to 40-m-thick cycle should have a period between 133 ky and
533 ky. Given that the highest amplitude astronomical cycle is the
405-ky eccentricity cycle, the 20- to 40-m-thick cycles of the
Haojiagou and Badaowan formations are most simply interpreted
as sedimentological expressions of that cycle. The 405 ky is the
most stable of the orbital cycles over geological time and is the
most appropriate term for the calibration of Mesozoic astrochronological age models (20, 21). Not only is it unimodal in
value, it is the least effected by chaotic diffusion of the gravitation
system of the Solar System (20, 21) and is a prominent feature of
many deep-time sequences (21), particularly in the Triassic and
Jurassic (22–26). Therefore, we calibrate the prominent 34.5 m
and 37.2 m MTM periodicities of the Haojiagou and lower
Badaowan formations, respectively, at 405 ky to obtain an age
model for the LITH index. These thickness periodicities are near
Sha et al.
C
200.5
201.0
~400 ky
201.5
202.0
L
overlap
TOC
(wt. %) 405 ky
130 2600
meters 405 ky Lith Index
405 ky ~100 ky
400
120 2400
110
100
Newark & Hartford Basins, USA
20°-21° N paleolatitude
2200
H26r
H26n
H25r
1800 AQ2r
90
1600
70 1200
1000
60
800
50
600
40
30
20
10
0
H24r
AQ1r
550
400
200
650
0 2 4 6 81012
Marl
Oil Shale
Carbonate
200.0
200.5
600
0
-200
199.5
H25n
500
80 1400
Ma
199.0
450
2000 AQ3r
polarity
H27n
700
H. Fm.
0
40
80
120
H24n/
(E24n)
201.0
(E23r)
(E23n)
Red
Purple
Gray
Black
Clastic
Rocks
200.0
W
199.5
TRIASSIC
Rhaetian
maximum deviation of solutions
199.0
JURASSIC
Hettangian
Sinemurian
GSSP
PlanLiasicus
S. angulata
Bucklandi
orbis
Blue Lias Formation
198.5
E. Quantoxhead section
meters kyr polarity
St. Audrie’s Bay section
405 ky ~100 ky Ma
D
Junggar Basin, China
60° N paleolatitude
201.5
Basalt
flows
Fig. 2. LITH Index data (C) and correlative sections: (A) Laskar 2010d solution (21); (B) Bristol Channel (United Kingdom); (C) Junggar Basin (China); (D) the Newark–
Hartford astrochronology and geomagnetic polarity time scale (APTS). The thick red bar indicates the interval of extinctions and uncertainty of correlations between
the sections, and the green arrows indicate the last appearance of L. rhaeticus (SI Text). A and B are adapted from refs. 19 and 31 (potential error added from ref.
21); D is modified from refs. 25 and 26. Note the difference in phase between the phasing eccentricity cycles in the La2010d solution (selected by ref. 31 for
comparison with B) and the geological data that we attribute to chaotic drift; therefore, we have retained the independent times scales for both A and D.
the middle of the 20- to 40-m range of the fluctuating band of high
amplitude in the wavelet spectra (Fig. 4 and Fig. S4).
Assuming that we have correctly identified the 405-ky cycle in
the LITH index depth series, the most prominent higher frequency
cycles of the Haojiagou and lower Badaowan formations have
spectral peaks with periods of between 30 ky and 60 ky, with the
median periods most strongly at 42.5 and 44.6 ky. These periods are
close to what would be expected for the obliquity periods, which for
the Triassic–Jurassic should be 36.6 and 46.7 ky (6, 27, 28), assuming a constant rate of recession of the moon and constant dynamic ellipticity of the Earth, with the former period being of much
higher magnitude. The shift to lower frequencies from the expected
precession and obliquity periods is also observed in the precession
band in the eastern North American Triassic Lockatong Formation
where the shift has been interpreted as a consequence of accumulation rate variability (22, 24). The most dramatic expression of such
a frequency-modulated shift would be occasional and perhaps periodically spaced hiatuses as might be present in the fluvial portions
of the Junggar sequences. However, it is not impossible that the
unexpectedly low frequencies could be real, caused by nonlinear
changes through time in dynamic ellipticity that could produce occasional decreases in precession rate (20, 29). Nonetheless, because
the independently U-Pb–calibrated (2) periods of Newark Basin
latest Triassic–Early Jurassic precession-band cycles are compatible
with an average period of about 20 ky, spectral distortion from
frequency modulation is the simpler explanation for the apparent
discrepancy. Relatively less important in the analysis are periods
that could be assigned to climatic precession although significant
periods are present in the MTM analyses. The weakness in amplitude at precessional periods could be a real feature of the climate
system of the Mesozoic (see Mesozoic High- vs. Low-Latitude
Cyclicity) or it could be due to accumulation rate noise at the
precessional frequencies. Periods at about 100 ky, although present,
are weak, consistent with the low power of the assumed precession
Sha et al.
periods, but, because we seem to be able to recognize the 405-ky
cycle, some climatic precession signal is evidently present.
Based on our analysis of thickness periodicities, the sedimentary
cycles attributed to climatic precession, obliquity, and eccentricity
cycles correspond to the microcycles and different scales of mesoscale cycles of Hornung and Hinderer (14). These Junggar Basin
strata are similar to what Olsen and Kent (30) termed Kap Stewarttype lacustrine sequences, named after the eponymous gray and
black cyclical strata of Jamesonland East Greenland (16). We
propose that the cycles in these sequences fit into a continuum of
orbitally forced lacustrine sedimentary cycles extending from the
tropics to the high latitudes, with the Haojiagou and Badaowan
cycles in Kap Stewart-type lacustrine sequences representing the
humid high latitude end member of the cyclicity (30). This type of
lacustrine sequence and cycles may well extend to the paleo-north
pole, for which there is obviously no sedimentary analog today.
Testing the Junggar Basin Age Model
Direct age calibration of the section by radiometric or paleomagnetic means does not yet exist for the Triassic–Jurassic of the
Junggar Basin; however, the age model may be at least partially
tested by its consistency with contemporaneous records from
elsewhere, specifically the Newark–Hartford basins of eastern
North America, the Bristol Channel Basin of the United Kingdom, and the Pucara Basin of Peru (Fig. 1, Fig. S3, and Table 1).
To compare the obliquity-dominated successions of the Junggar
Basin with the precession-dominated eastern North American lacustrine sequences and the contemporaneous marine
section at St. Audrie’s Bay in the United Kingdom (Bristol
Channel Basin), we compared the filtered 405-ky cycle from the
three sections (SI Text) and correlated them using the last appearance of Lunatisporites rhaeticus (green arrows in Fig. 2).
Using the latter datum results in the encouraging observation
that the 405-ky cycles are in phase and that the interval of low
PNAS Early Edition | 3 of 6
EARTH, ATMOSPHERIC,
AND PLANETARY SCIENCES
Bristol Channel Basin, UK
31° N paleolatitude
M. Badaowan
Fm.
B
Eccentricity
Solution La2010d
Lower Badaowan Formation
A
10.0
5.0
3.3
2.5
2.0
1.7
abcd
1.4
1.3
1.0 period m
1.1
Badaowan Fm.
Junngar Basin
60°N at 201 Ma
g h
ef
i
1.0
j
f - test
Clipped LITH Index
Spectral Power 435-690 m
A
0
B
0.1
Color Series
Spectral Power 0-1866 m
a
100.0
0.2
0.3
50.0
0.4
0.5
33.3
25.0
0.6
0.7
20.0
16.7
0.8
14.3
12.5
g
f
e
1.0
h
ij
0.9
0
Depth Rank
Spectral Power 2767.6-3369.6 m
D
0.02
0.03
0.04
0.05
100.0
50.0
33.3
25.0
20.0
200.6 - 201.2 Ma
Newark Basin
20°N at 201 Ma
0.08
frequency cycles/ m
16.7
14.3
12.5
period m
g
h
1.0
d
c
f - test
b
0.07
f
e
a
409.6m/405.0ky
124.8m/123.4ky
95.0m/93.9ky
60.4m/59.7ky
47.3m/46.8ky
31.4m/31.1ky
24.0m/23.8ky
22.6m/22.4ky
21.5m/21.3ky
20.4m/20.2ky
0.06
a.
b.
c.
d.
e.
f.
g.
h.
364.1 ky
91.0 ky
46.8 ky
33.4 ky
24.8 ky
19.7 ky
18.7 ky
16.1 ky
0.9
0
0
10.0
20.0
20.0
10.0
30.0
7.7
40.0
5.0
50.0
4.0
d
60.0
3.3
2.9
70.0
2.5
g
e f
0.05
2.2
frequency cycles/ m
period m
Lockatong Fm.
Newark Basin
5°N at 222 Ma
a,b c
0
80.0
0.10 0.15
1.0
h i
f - test
Depth Rank
Spectral Power 200.6-201.2 Ma
C
0.01
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
period m
f - test
c d
253.6m/2977.1ky
69.8m/818.9ky
34.5m/405.0ky
20.0m/234.7ky
8.8m/103.3ky
7.7m/90.4ky
4.8m/56.4ky
3.8m/44.6ky
2.1m/24.7ky
2.0m/23.5ky
0.9
0.9 1.0 frequency cycles/ m
Portland Fm.
Hartford Basin
21°N at 200 Ma
a b
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
0.20
0.25
0.30
0.35
0.40
a.
b.
c.
d.
e.
f.
g.
h.
i.
159.8m/875.5ky
73.9m/405.0ky
22.8m/124.9ky
17.4m/95.4ky
8.4m/46.0ky
6.7m/36.7ky
5.5m/30.1ky
4.6m/25.2ky
3.9m/21.4ky
astrochronologies, with the marine ammonite-based ETE and
Hettangian–Sinemurian boundary in complete agreement (within
tight error) with the Newark–Hartford and Bristol Channel
astrochronologies (Fig. 2 and Table 1). This framework of multiple
independent constraints strongly supports the Junggar Basin
astrochronology.
Mesozoic High- vs. Low-Latitude Cyclicity
The Haojiagou and Badaowan formations are, to our knowledge,
the first high-latitude early Mesozoic continental sequences for
which astronomical forcing has been quantitatively explored,
and, unlike contemporaneous lower-latitude analyses, obliquitypaced cyclicity is a dominant high-frequency component of the
variability. A comparison of MTM spectra and wavelet spectra
from the high-latitude Badaowan Formation and the lower latitude
continental sequences in eastern North America shows this difference dramatically (Fig. 4). The lower latitude records for both
Triassic and Jurassic have little obliquity signal and are strongly
dominated by climatic precession corroborated by the independent
U-Pb and magnetostratigraphic tests (2, 31) (Fig. 2 and Table 1).
Obliquity-related insolation variation is greatest at high latitudes, but dominance of obliquity in climate is not necessarily
expected as a consequence. In theory, interannual insolation
forcing at a given calendar day or yearly average is dominated by
precessional cycles at all latitudes, even at the poles where the
obliquity effect on insolation variation is the greatest (32).
However, obliquity dominance in high-latitude climate is by no
means without precedent, the most spectacular example of which
is the dominance of 41-ky glacial cycles of all but the last
0.8 million y (3.0–0.8 Ma) of the Neogene (33) and is also an important component of variability in the high-latitude (∼52–55° N)
Lake Baikal sedimentary record (34) situated at a similar latitude
to the Junggar Basin deposits.
Differences between the Late Neogene world and that of the
Triassic–Jurassic are vast, including but not limited to continental
0.9
0.45 frequency cycles/ m
Fig. 3. MTM spectra from high and low Triassic–Jurassic latitudes: (A) highlatitude Badaowan Formation, Junggar Basin, China; (B) contemporaneous
low-latitude Portland Formation, Hartford Basin, eastern United States;
(C) contemporaneous low-latitude Newark Basin Towaco and Boonton formations, eastern United States; and (D) equatorial Lockatong Formation,
Newark Basin, eastern United States (modified from ref. 22), showing that
the low-latitude low obliquity signal is not limited to the Triassic–Jurassic
boundary interval. Spectra are lined up by time based on the 405-ky cycle.
Highlighted spectral peaks are only those with both high amplitude and
high f-test significance (>0.9) (red). The area between the upper and lower
confidence limits is shaded gray. Note that, for A, B, and D, accumulation
rate is based on setting a specific spectral peak to 405 ky whereas, in C,
accumulation rate is derived from U-Pb dates and tuning to a 20-ky average
climatic precession cycle (2). See SI Text for details.
variance interpreted as a minimum in the long eccentricity g4 − g3
cycle (2, 19, 31) occurs in same relative position (Fig. 2).
The Newark–Hartford astronomical calibration was independently
corroborated using U-Pb dates from interbedded lavas (2) and
could be confidently and tightly correlated to marine sections.
Tying the Newark–Hartford and Bristol Channel Basin astrochronologies at the biostratigraphic ETE with a U-Pb–determined
age of its base at 201.564 ± 0.015 Ma (2) (from the Newark–
Hartford section) provided near perfect agreement between the
magnetostratigraphy of the two areas, as well as with the astrochronological ages of the Hettangian–Sinemurian boundary, the
formal definition of which (GSSP, global boundary stratotype
section and point) is within the Bristol Channel sequence (31)
(Table 1). The Pucara Basin section contains multiple dated ashes
(ref. 17 and references therein, allowing further testing of the
4 of 6 | www.pnas.org/cgi/doi/10.1073/pnas.1501137112
Fig. 4. Untuned (depth) wavelet spectra of the LITH data of high-latitude
Haojiagou and Badaowan formations of Rhaetian to Sinemurian age (Late
Triassic–Early Jurassic, Junggar Basin) with strong power in the obliquity
band (∼40 ky) and low power in the climatic precession (∼20 ky) band
compared with the low-latitude Lockatong Formation of Norian (depth
rank, Late Triassic, Newark Basin) (from ref. 28). Spectra are lined up along
the frequency modulations (in thickness) of the 405-ky cycle. Similar continuous data for the Rhaetian–Sinemurian of eastern North America are not
available. Lower and upper green arrows for the Junggar Basin indicate the
end-Triassic extinction (201.6 Ma) and the Hettangian–Sinemurian boundary
(199.7 Ma), respectively (Figs. S3 and S4).
Sha et al.
Table 1. U-Pb and astrochronological ages compared
Boundary or unit
Hettangian–Sinemurian boundary
Hook Mountain Basalt
Preakness Basalt
Rhaetian–Hettangian boundary
Orange Mountain Basalt
End-Triassic extinction
Newark igneous*
—
200.916 ±
201.274 ±
—
201.520 ±
201.564 ±
0.064
0.032
0.034
0.015
Newark–Hartford*
Pucara Basin
Bristol Channel†
Pucara‡/Newark§
±
±
±
±
±
±
199.46 ± 0.17
—
—
201.36 ± 0.14‡
—
201.51 ± 0.15
199.61/199.66
—
—
201.32/201.37
—
201.51/201.56
199.70
200.93
201.28
201.42
201.52
201.56
0.02
0.02
0.02
0.022
0.02
0.02
configuration with Pangea straddling the equator, a lack of polar
glaciers (35), and very high CO2 (approximate background at between
1,000 and 2,000 ppm and maxima of >6,000 ppm) (36)—a world
without modern analog. Therefore, explanations of obliquity
dominance due to fluctuations of high-latitude glaciers are difficult to support for the early Mesozoic. However, some aspects
of these explanations might still be pertinent to the Haojiagou
and Badaowan formations. In particular, integrated summer insolation is directly controlled by obliquity and has been proposed
as a cause of the late Neogene obliquity dominance in glacial
fluctuations (32), and it is possible that the highly vegetated Triassic–Jurassic high latitudes were similarly sensitive to the length
of the growing season and associated timing and magnitude of
precipitation and evaporation.
Implications for Chaotic Evolution of the Solar System and
Astronomical Solutions
Since Poincaré’s (37) contribution to dynamical systems, it has
been recognized that the Solar System has chaotic properties.
Chaos significantly limits the accuracy of numerical solutions of
planetary behavior, including the frequency and phases of climatically important orbital cycles (4–6), and impedes understanding of
the general problem of the stability of the Solar System (5, 13). At
time scales of hundreds of millions of years, chaotic diffusion of the
gravitational system of the Solar System results in an inability to
recognize accurate solutions of planetary orbital and axial behavior (4).
Integral to the long-term chaotic behavior of the Solar System
are the secular resonances of the planets, particularly for the
inner Solar System. Particularly important are those of Earth and
Mars (4), affecting modulations of eccentricity and obliquity with
present periods of 2.4 and 1.2 My (g4 − g3 and s4 − s3, respectively, where g4 and g3 are related to the precession of the
orbital perihelia of Mars and Earth and s4 and s3 are related to
orbital inclination). However, due to chaotic diffusion of the
gravitational system, these periods are expected to change through
time. Presently, there is a two-to-one ratio of the eccentricity
modulator (2.4 My) to the obliquity modulator (1.2 My), reflecting
the secular resonant argument 2(s4 − s3) − (g4 − g3) = 0, which is
currently in libration. However, there are expected to be important transitions in the chaotic behavior of the gravitational system
from libration to circulation so that the eccentricity and obliquity
modulators are equal (s4 − s3) − (g4 − g3) = 0 (38). Because both
the period and state of these modulating cycles have varied in an
unknown way in deep time, strict interpretation of insolation
curves are unreliable beyond about 50 Ma (20, 21). This uncertainty is most obviously reflected in the eccentricity and
obliquity modulating cycles with periods longer than 405 ky and
the long-term phase relationships of all of the cycles. Without
geological data with a long obliquity record, it is not possible to
determine when these transitions in the Earth–Mars resonances
Sha et al.
occur or even if they occur, or what the periods of the long eccentricity or inclination cycles should be.
In addition to being a celestial mechanical problem, chaotic
drift in the gravitational solutions also poses fundamental Earth
science problems because it limits tuning of geological records to
insolation curves and our ability to use astrochronologies to assess and improve the accuracy of important isotopic dating systems (e.g., ref. 39). Empirical, deep-time geological data have
the potential to allow us to determine which solutions best fit the
actual history of the Solar System.
To quantify the actual behavior of the celestial mechanical
gravitational system, precession-related (eccentricity) and obliquityrelated cycles need to be isolated in geological records. Continental records, which tend to be tightly coupled to local forcing,
provide a possible mechanism to isolate precession-related eccentricity cycles, dominant at low latitudes, from the obliquityrelated cyclicity important at higher latitudes.
Previous quantitative investigations of long Late Triassic–
Early Jurassic records have been limited to the lower latitudes,
largely the tropics and subtropics in eastern North America (2,
22, 24, 25) and the United Kingdom (e.g., refs. 19 and 40). In
these areas (20°–30° N) (10), the effects of obliquity on local
climate forcing would be expected to be small compared with the
higher latitudes, as predicted by basic astronomical theory, although precessional effects should always be greatest in insolation at all latitudes, and that is what is observed for the
Triassic–Jurassic in the records described thus far. In the case of
the tropical records in eastern North America, obliquity was
barely detected (22, 24), but a strong 1.6- to 1.8-My cycle in
eccentricity (g4 − g3) is present, differing from the present 2.4 My
presumably because of chaotic diffusion (6, 24). More or less
the same value of the g4 − g3 cycle, in the same phase, is present
in the contemporaneous tropical pelagic cherts from the Panthalassic Ocean at Inuyama, Japan (41).
Until now, there have been no long Triassic–Jurassic, highlatitude records that have been quantitatively analyzed, and
therefore we have had little knowledge of what the quantitative
obliquity behavior was, especially with regard to their modulating
cycles. Importantly, there is a strong suggestion of modulation of
the obliquity by an ∼819-ky (∼70-m) cycle in the upper Haojiagou
and lower Badaowan, visible in the wavelet spectrum (Fig. 3 and
Fig. S4) where it is evident as a modulation in the strength of
obliquity cycle (Fig. S4), both as filtered and demodulated data
(Figs. S5–S7), and also as period in its own right (Fig. S4). This
period is missing or extremely weak in the tropical continental
records (22, 24). Together, the data from the Junggar Basin,
Newark–Hartford basins, and St. Audrie’s Bay section suggest the
present-day two-to-one ratio (Early Jurassic, ∼1.6–0.8 My) of orbital eccentricity to inclination for the state of the Earth–Mars
resonance, but with different periods and phases not seen in
existing orbital solutions (21) (Fig. 2).
PNAS Early Edition | 5 of 6
EARTH, ATMOSPHERIC,
AND PLANETARY SCIENCES
*See ref. 2 for ages. Details in Table S2.
†
See refs. 19 and 31 for ages. Details in Table S2.
‡
See refs. 12 and 17 for ages. Details in Table S2.
§
See ref. 15 for ages. Details in Table S2.
Conclusions
Analysis of the LITH proxy of environmental change shows that
an astronomical signal in which obliquity is dominant can be
extracted from lacustrine strata of the high-latitude (∼60° N)
Junggar Basin straddling the end-Triassic extinction and Triassic–
Jurassic boundary. Constrained by fixing the accumulation rate to
the 405-ky eccentricity cycle, data show that the main periods of
obliquity for the Late Triassic–Early Jurassic are present and were
dominant components of high-latitude Early Mesozoic climate,
dramatically different from the climatic precession-dominated
continental tropics. In combination, the data are incompatible with
published astronomical solutions for the Triassic–Jurassic in phase
and amplitude, consistent with chaotic behavior of the Solar System
whereas, at the same time, the Earth–Mars orbital resonance seems
to have been in today’s two-to-one ratio of eccentricity to inclination,
providing a constraint for the Earth–Mars secular resonance for
around 201 Ma. With the prospect of the acquisition of better
temporally resolved records from deeper lake settings in the Junggar
and other basins, the use of more directly climate-sensitive proxies,
and additional exploration of the paleobiological context of the
strata, it will be possible to test these findings, constraining the history
of Solar System chaos, during this transitional time in Earth history.
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Methods
LITH index data were recorded during the 1996, 1998, and 2008 field seasons
using standard descriptive field methods. Standard preparation procedures
were used to prepare the palynological slides, archived at the Department of
Geology, Lund University, Sweden. The evolutive FFT and MTM spectra were
developed using Analyseries (2.0) (42), and the evolutive wavelet spectra were
computed using the Matlab script of Torrence and Compo (43). See SI Text
for additional methodological details.
ACKNOWLEDGMENTS. We thank Deng Shenghui for helpful comments in
the field and on the manuscript and Dennis Kent for help in interpreting
the paleolatitude of the basin. We are grateful to Ji Xuefeng and Cheng
Xiansheng, who guided us in fieldwork and shared significant unpublished
information. We thank Christopher Scotese for help in producing the
reconstruction of Pangea in Fig. 1. The manuscript was reviewed by Linda
Hinnov and Michael Rampino, who provided many useful suggestions. Research was supported by the National Basic Research Program of China (973
Program 2012CB821906), the Strategic Priority Research Program (B) (Chinese
Academy of Sciences XDB03010101), National Natural Science Foundation
of China (91114201), Bureau of Geological Survey of China, the National
Committee of Stratigraphy of China, and the Linnaeus Centre, Lund University Carbon Cycle Centre (LUCCI) funded through the Swedish Research
Council (349-2007-8705). This article is a contribution to United Nations Educational, Scientific and Cultural Organization-International Union of Geological Sciences-International Geoscience Programme (UNESCO-IUGS-IGCP)
Project 632.
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Sha et al.
Supporting Information
Sha et al. 10.1073/pnas.1501137112
SI Text
Paleogeographic Reconstruction. The illustration of Pangea in Fig. 1
and Fig. S1 was redrafted from a reconstruction for the Triassic–
Jurassic transition (201.6 Ma) produced by the PALEOMAP
Project (1–3) displayed using GoogleEarth. The positions of the
Pucara (Peru), Newark–Hartford (United States), Bristol Channel
(United Kingdom), and Junggar (Western China) basins on Pangea
were then translated as rigid plate south about 3° along the prime
meridian to bring their paleolatitude into agreement with ref. 4.
This slight reconfiguration produced virtually no change in the
latitude of the Junggar Basin at about 60° N from the PALEOMAP
reconstruction.
A 60° paleolatitude for the Junggar is in agreement with several additional lines of evidence. Paleomagnetic determinations
of paleolatitude of Triassic–Jurassic strata from Junggar and the
adjacent Tarim Basin (e.g., ref. 5), although scarce and wholly
from sedimentary rocks, suggest a paleolatitude close to that of
the present 45° N. The existing paleomagnetic literature, however, does not take into account the effects of compactioninduced inclination error (4, 6, 7), which is greatest at the latitudes
suggested by Carroll et al. (8) for the Junggar Basin. Correcting
for paleomagnetic inclination error has proved crucial in reconciling discrepant igneous and sedimentary paleomagnetic data in
Eastern North America and Greenland (6) in strata correlative to
those discussed here, and a approximate correction of 10–15° of
paleolatitude is plausible for the Junggar Basin, an estimate of
which can be tested by the collection of additional paleomagnetic data. Carroll et al. (8) show similarly high latitude for the
basin (∼60° N) based on the plate-tectonic context. The estimated position of 60° N as shown in the PALEOMAP reconstructions is therefore plausibly the best available estimate
of latitude (Fig. 1).
Location of the Haojiagou Section. The Haojiagou and Badaowan
formations outcrop more or less continuously in badlands along
the Haojiagou (gou = valley) located at about 50 km southwest of
Ürümqi City on the southern margin of the Junggar Basin of the
northern Xinjiang Uygur (Uighur) Autonomous Region, Northwestern China (Figs. 1 and 2 and Figs. S1 and S2). About 1,100 m
of this section is the basis of this report, beginning at ∼43° 38.452’
N, 87° 13.266’ E and ending 43° 39.889’ N, 87° 12.170’ E. The
section has been studied in various aspects (e.g., refs. 9–16), but
only one summary on the cyclostratigraphy has been published to
date (17). The data presented here were collected on the east side
of the valley.
Construction of the LITH Index. The Haojiagou section was described by Deng et al. (18), with the lithologic data being collected and obtained during fieldwork in 1996, 1998, and 2008.
The initial analysis is distinguished by the thickness and lithologic features, reflecting the paleoenvironment, of each measured layer. By using the semiquantitative classification of lithology
called the “LITH” index (19), a hierarchy of cycles based on
sedimentary rock types was recognized, and the different digital
numbers (LITH values) were defined for various rock types
(Table 1). The variations (values between 10 and 130) in LITH
produce the obvious cyclicity. We converted two measurements
(depth measurements and LITH measurement), by interpolating
a LITH value at 0.1-m intervals within each layer, into a numerical time series forming a new time series, LITH time series,
on which our times series analyses were performed (Fig. S3).
Sha et al. www.pnas.org/cgi/content/short/1501137112
Temporal Constraints on the Junggar Latest Triassic and Earliest
Jurassic Strata. Forty samples spanning the boundary of the
Haojiagou and Badaowan formations, Junggar Basin, China were
examined for palynology. Of these samples, 35 were usefully
productive samples (Fig. S3) and formed the basis of the range
chart shown in Fig. 3. Our analysis focuses on the ETE, supercedes
the palynological analysis in Sha et al. (15), and includes more
samples for higher resolution. Samples were processed at Global
GeoLab Ltd., Canada (www.globalgeolab.com) following standard
methods. The palynological slides and residues are stored at the
Department of Palaeobiology, Swedish Museum of Natural History.
The sedimentary successions of the Haojiagou and Badaowan
formations at the Haojiagou section yielded well-preserved
miospore assemblages of medium diversity; 60 species of fossil
pollen and spore taxa were identified in this study, together with
a putative dinoflagellate (Chytroeisphaeridia sp.) and the chlorophyte (green alga) Botryococcus braunii. The age assessment is
based on a combination of last and first appearance datums for key
taxa (Fig. S3). Typical Triassic elements persist up to bed 52, including Lunatisporites rhaeticus and Limbosporites spp., whereas the
abundant occurrence of Retritriletes semimuris and Retritriletes austroclavatidites in bed 53 suggests a Hettangian age (20), and the end
of the ETE interval (Fig. 3 and Fig. S3).
The presence of Cerebropollenites macroverrucosus and Callialasporites trilobatus in bed 81 suggests a Sinemurian–Pliensbachian age (21) for that level. The comparison with European
and Australian palynostratigraphical schemes is tentative because these regions represent different floral paleo-provinces
from those previously described for this region (9, 12) and because correlative zonation schemes between the regions have not
been erected. Identification of the Hettangian–Sinemurian boundary to the Haojiagou section is more problematic because there is
apparently no change in sporomorph composition across that
boundary at the base-Sinemurian GSSP in the United Kingdom or
Europe in general (22–24).
Thus, based on the palynology, we have placed the top of the
extinction interval, still in the late Rhaetian, at the last appearance datum (LAD) of the taeniate gymnosperm pollen L. rhaeticus.
This sporomorph is regarded as a near-end-Rhaetian marker in
Europe (including the United Kingdom), Greenland, and Eastern
North America (25–29), where its last appearance occurs close to
and above the initial expression of the end-Triassic extinction. In
Eastern North America, the last appearance of this pollen taxon
occurs in strata about 60 ky younger than the initiation of the
initial ETE, as constrained by both U-Pb dates and astrochronology (30), and the Triassic–Jurassic boundary occurs about 40 ky
after that based on extraopolation and correlation with United
Kingdom sections (31). Thus, we use the LAD of L. rhaeticus
as a tie point to pin the ETE within the studied successions
(Figs. 2 and 3).
In terms of floral provinces, Sun et al. (ref. 13 and references
therein) argue that the Haojiagou (Late Triassic) floral assemblage belongs to the Danaeopsis–Symopteris assemblages [updated
from the original Danaeopsis–Bernoullia assemblage because the
latter name has a prior synonym that is a malvaceous angiosperm
(Bombacaceae)] (32), “Northern China” continental floristic province whereas the Badaowan (Early Jurassic) florules belong to the
Coniopters–Phoenicopsis or “Siberian” continental floristic province,
both of which are typical northern-hemisphere, high-latitude humid
assemblages. The transition between the Danaeopsis–Symopteris and
Coniopters–Phoenicopsis assemblages around the Triassic–Jurassic
transition is interpreted as indicating a transition to more humid
1 of 8
S4 and S5) were developed using Analyseries (2.0) (41), and the
evolutive wavelet spectrum was computed using the Matlab script of
Torrence and Compo (42) (paos.colorado.edu/research/wavelets/).
For all data, the original depth series was interpolated with an increment of 0.1 m. Data were divided into two series: a low LITH
index series with values from 20 to 60, which were then reversed
and rescaled to range from 0 to 40 (with 40 being fine grained and
0 being coarse), and a high LITH index series with values from 60 to
140 (with 60 being fine grained and 140 being coarse). For the
MTM spectra the following Analyseries options were used: linear
trend was removed, medium confidence vs. resolution was selected,
width.ndata product was 4, six windows were used, output was
resampled from 0 to 2 with a step of 0.001, and inferior and
superior error bars and amplitude spectra were computed (for
Fig. 4 and Fig. S4). For the FFT, periodograms (power spectra)
were prepared with the following Analyseries options: linear
trend was removed, Bartlett window was used, and output was
resampled from 0 to 2 with a step of 0.001. Note that Analyseries
does not use adaptive weighting and thus tends to overestimate
the number of significant harmonics in frequencies with low
power. Consequently, we regarded only cycles with high power
and high f-test statistics as having been meaningful. For the
405-ky filtered clipped-LITH data, a frequency of 0.0289855 m
per cycle was used with a bandwidth of 0.005, with a Gaussian
shape. For the 405-ky frequency of the total organic carbon
(TOC) data of ref. 38, a frequency of 0.00062486 cm per cycle
was used with a bandwidth of 0.0003 and a Gaussian shape. The
modulation of obliquity (Fig. S7) is based on bandpass filtering
the clipped LITH series with a 0.275 m per cycle frequency and
a bandwidth of 0.02 and a Gaussian shape, which was then demodulated [amplitude modulated (AM) filtered]. The result was
compared with a bandpass filtering of the clipped LITH series at
a frequency of 0.0142857 m per cycle and a bandwidth of 0.01
and a Gaussian shape. The wavelet spectra were computed using
the Matlab script of Torrence and Compo (42) (paos.colorado.
edu/research/wavelets/software.html) with dt = 0.1 and all other
options at the default values.
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14. Hornung J, Hinderer M (2011) Depositional dynamics and preservation potential in
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and warm conditions (13). Generally, warm and humid conditions
in both formations are consistent with the broad-leaf gymnosperm
assemblage and the presence of common coal and are consistent
with many sedimentary basins in the early Mesozoic northernhemisphere high latitudes (33, 34) although they clearly represent
nonanalog communities and although it is very difficult to assess
whether these assemblages have any time significance.
In contrast, the numerical ages of the ETE are now well-understood at 201.564 ± 0.015 Ma (30), the Triassic–Jurassic boundary
between 201.32 ± 0.13 Ma and 201.39 ± 0.14 Ma (35) [mean of
201.36 ± 0.14 Ma, rms error], and the Hettangian –Sinemurian
boundary at about 199.46 ± 0.17 Ma (corrected from the original
199.43 ± 0.10 Ma date of ref. 36), based on zircon 206Pb/238U
ages and astrochronology, with varying degrees of precision and
additional uncertainty (up to 0.1%) due to very slightly different
interlaboratory methods. The duration of the Hettangian is thus
now well-established, with the most recent estimates being 2 My
(U-Pb; ref. 37), 1.8 My (astrochronology; refs. 31, 38, and 39),
and 1.88 ± 0.16 My (U-Pb; refs. 30 and 36). These durations are
all close to the duration of 2 My for the Hettangian in the most
recent timescale compilation (40). Based on the U-Pb dates and
astrochronology in ref. 30, we used the last appearance of
L. rhaeticus to tie the Badaowan section at 201.50 ± 0.1 Ma
(Figs. 2 and 3 and Fig. S3).
Analytical Methods. The FFT and MTM spectra (Fig. 4 and Figs.
Sha et al. www.pnas.org/cgi/content/short/1501137112
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31. Whiteside JH, Olsen PE, Eglinton T, Brookfield ME, Sambrotto RN (2010) Compoundspecific carbon isotopes from Earth’s largest flood basalt eruptions directly linked to
the end-Triassic mass extinction. Proc Natl Acad Sci USA 107(15):6721–6725.
32. Kustatscher E, Pott C, van Konijnenburg-van Cittert JHA (2011) A contribution to the
knowledge of the Triassic fern genus Symopteris. Rev Palaeobot Palynol 165(1):41–60.
33. Lu B, Deng S, Qi X (2000) Jurassic climatic events of North China and their geological
significance. GeoResearch Forum 6:463–472.
34. Willis KJ, McElwain JC (2002) The Evolution of Plants (Oxford Univ Press, New York).
35. Wotzlaw J-F, et al. (2014) Towards accurate numerical calibration of the Late Triassic:
High-precision U-Pb geochronology constraints on the duration of the Rhaetian.
Geology 42:571–574.
36. Guex J, et al. (2012) Geochronological constraints on post-extinction recovery of the
ammonoids and carbon cycle perturbations during the Early Jurassic. Palaeogeogr
Palaeoclimatol Palaeoecol 346–347:1–11.
37. Schaltegger U, Guex J, Bartolini A, Schoene B, Ovtcharova M (2008) Precise U–Pb age
constraints for end-Triassic mass extinction, its correlation to volcanism and Hettangian post-extinction recovery. Earth Planet Sci Lett 267:266–275.
A
38. Ruhl M, et al. (2010) Astronomical constraints on the duration of the early Jurassic
Hettangian stage and recovery rates following the end-Triassic mass extinction
(St. Audrie’s Bay/East Quantoxhead, UK). Earth Planet Sci Lett 295:262–276.
39. Olsen PE, Kent DV, Whiteside JH (2011) Implications of the Newark Supergroup-based
astrochronology and geomagnetic polarity time scale (Newark-APTS) for the tempo
and mode of the early diversification of the Dinosauria. Earth Environ Sci Trans R Soc
Edinburgh 101:201–229.
40. Gradstein FM Ogg JG, Schmitz M, Ogg G, eds (2012) The Geologic Time Scale 2012
(Elsevier Science, Oxford).
41. Paillard D, Labeyrie L, Yiou P (1996) Macintosh program performs time-series analysis.
Eos Trans AGU 77:379.
42. Torrence C, Compo GP (1998) A practical guide to wavelet analysis. Bull Am Meteorol
Soc 79:61–78.
43. Maron M, et al. (2015) Magnetostratigraphy of the Pignola-Abriola section: new
constraints for the Norian/Rhaetian boundary. Geol Soc Am Bull, 10.1130/B31106.
B
Junggar
Basin
60
50°
Ürümqi
area
°
am
wm
Junggar Basin
am
tm
40°
tm
km
Beijing
km
Tarim Basin
Bristol Channel
Basin
Newark
Basin
20°
Pucara
Basin
equator
C
80°
87° 15'
90°
100°
87° 30'
110°
120°
Quaternary
Neogene
43° 50’
Paleogene
in
Xishan Mounta
in
Kalazha Mounta
Urumqui
Liuhuaggou
43° 40’
Tou
t
un
Riv
er
43° 45’
30°
r
ive
iR
mq
Uru
Cretaceous
Late Jurassic
Kalaza Fm.
Late Jurassic
Qigu Fm.
Late Jurassic
Toutunhe Fm.
Middle Jurassic
Xishanyao Fm.
Middle Jurassic
Sangonghe Fm.
Early Jurassic
Badaowan Fm.
Late Triassic Haojiagou
& Huangshanjie Fm.
Triassic
Permian
Carboniferous
aou
oji
Ha
Faults
Haojaigou Section
Fig. S1. Paleogeographic and present position of the Junggar Basin. (A) Paleogeographic position of the Junggar Basin, Bristol Channel, Newark–Hartford,
and Pucara basins with the distribution of the Central Atlantic Magmatic Province shown in darker tan. (B) Map of the Junggar and Tarim basins, Northwest
China (based on ref. 8). as, Altay Shan; ks, Kunlun Shan; ts, Tian Shan. (C) Map of the surficial geology of the Ürümqi area showing the position of the
Haojiagou section.
Sha et al. www.pnas.org/cgi/content/short/1501137112
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Fig. S2. Images of the Junggar Basin section. (A) GoogleEarth image of Haojiagou section (red box), the location of which is shown in Fig. S1, showing
relatively undeformed strata tilting to the north-northeast. (B) Photograph of portion of the Haojiagou section including beds 45–53, looking west across the
valley. The section was measured on the east side of Haojiagou from where the photograph was taken.
Sha et al. www.pnas.org/cgi/content/short/1501137112
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Fig. S3. Measured LITH index, simplified stratigraphic column, bed numbers, biostratigraphic data, and age model for the Haojiagou section. The occurrences
of taxa are shown by ticks based on new counts, on which the new sporomorph assemblages are based. The red line marks the top of the range of L. rhaeticus
in our studied section, the marker taxon used to correlate the lower Badaowan Formation to the eastern North American and United Kingdom sections (Fig. 4).
The numerical ages in the age model are based on recognition of the 405-ky cycle in the MTM spectra, with the ages indicated in red representing the
projections into the section of the initial end-Triassic extinction (201.6 Ma) and the Hettangian–Sinemurian boundary (199.7 Ma; thicker red bar indicated
uncertainty from Fig. 4), and the Norian–Rheatian boundary date is based on the Newark–Hartford APTS (interpreted by ref. 43) and the independent 206Pb/238U
zircon Pucara Basin ashes (35). Gray fill in the standard ages indicates the range of possible boundary picks internal to data from the Junggar Basin itself, and the
dashed lines indicate stage boundaries as suggested in ref. 17. The δ13C data are from ref. 33. All data are registered to the bed numbers as measured by this field
party in the Haojiagou section.
Sha et al. www.pnas.org/cgi/content/short/1501137112
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period (m)
2.5
1.7
de
f
h
i
0.2
10.0
5.0
300
a.
b.
c.
d.
a
0.4
0.5
0.6
0.7
3.3
2.5
2.0
1.7
1.4
41.0m/405.0ky
15.8m/156.1ky
10.2m/100.8ky
7.06m/69.74ky
0.2
5.0
c
b
700
e
a
f
Haojiagou Fm.
800
0
a.
b.
c.
d.
e.
f.
g.
h.
900
0.1
0.2
0.3
0.4
0.5
5.0
3.3
2.5
2.0
a
d
1000
20
140
a.
b.
c.
d.
e.
f.
g.
h.
c
e
204.8 102.4 51.6 25.6 12.8 6.4 3.2 1.6
period (m / cycle)
0.8
0.6
1.7
0.7
1.4
f
0.8
1.3
34.1m/405.0ky
20.5m/243.5ky
6.02m/71.50ky
3.79m/45.01ky
3.20m/38.01ky
2.18m/25.89ky
1.75m/20.78ky
1.35m/16.03ky
g
10.0
b
0.1
0.2
0.3
0.4
1.0
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
10.0 5.0
3.3
2.5
2.0
1.7
1.4
1.3
1.1
1.0
a.
b.
c.
d.
e.
f.
i
g.
j h.
i.
j.
0.6
0.7
1.4
0.8
1.3
34.1m/405.0ky
7.88m/93.59ky
4.36m/51.78ky
3.94m/46.79ky
3.06m/36.34ky
2.20m/26.13ky
1.83m/21.73ky
1.43m/16.98ky
g
0.5
frequency (cycles/m)
0.7
1.0
0.1
0.2
0.3
0.4
0.5
0.6
10.0 5.0
3.3
2.5
2.0
1.7
a
b
h
g
c
d
0.1
0.2
e
f
a.
b.
c.
d.
e.
f.
g.
h.
0.7
0.8
0.9
1.0
1.4
1.3
1.1
1.0
37.2m/405.0ky
17.1m/186.1ky
7.9m/88.0ky
4.7m/51.2ky
3.9m/42.5ky
3.1m/33.8ky
2.4m/26.1ky
1.9m/20.7ky
1.0
9501035
m
h
0.6
253.6m/2977.1ky
69.8m/818.9ky
34.5m/405.0ky
20.0m/234.7ky
8.8m/103.3ky
7.7m/90.4ky
4.8m/56.4ky
3.8m/44.6ky
2.1m/24.7ky
2.0m/23.5ky
0.9
h
1.7
ef
0.9
0
0.1
1.0
0.2
abcd
0
0.4
0
1.1
0.9
0
i
0.5
2.0
d
1.3
1.3
g h
0.4
2.5
1.4
64.3m/405.0ky
16.5m/103.9ky
10.2m/64.3ky
6.8m/42.9ky
5.3m/33.4ky
3.7m/23.3ky
3.2m/19.9ky
2.4m/15.1ky
0.8
e. 3.66m/36.15ky
f. 3.41m/33.68ky
g. 2.38m/23.51ky
h. 2.18m/21.55ky
i. 1.90m/18.77ky
h
600
L
Norian Rhaetian
h
de
g
0.3
3.3
a.
b.
c.
d.
e.
f.
g.
h.
b
power
0.1
10.0
1.7
f
435-690 m
lower
0
2.0
c
c d
f
2.5
g
0.3
203.0
206.0
3.3
a
j
b
400
202.0
205.0
205.4
10.0 5.0
1.3
305-435 m
0.1
e
204.0
1.4
f. 4.55m/26.98ky
g. 3.66m/21.71ky
h. 3.25m/19.28ky
i. 2.41m/14.29ky
j. 2.13m/12.63ky
g
500
201.6
period (m)
2.0
68.3m/405.0ky
20.5m/121.6ky
17.1m/101.4ky
10.8m/64.04ky
7.59m/45.01ky
200
0
Hettangian
201.0
upper
Sinemurian
199.0
199.7
200.0
c
Badaowan Fm.
middle
198.0
3.3
a.
b.
c.
d.
e.
b
100
197.0
5.0
f - test
10.0
a
f - test
196.0
f - test
0.005 0.010 0.020 0.039 0.156 0.313 0.625 1.250 2.500
204.8 102.4 51.6 25.6 12.8 6.4 3.2 1.6 0.8 0.4
0
power
140
MTM Spectra
selected intervals
0-305 m
20
frequency (cycles / m)
period (m / cycle)
690-950 m
Ma
FFT Spectra
selected intervals
Wavelet Spectrum
Lithologic
Index
power
Age and Units
0.8
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
frequency (cycles/m)
Fig. S4. Wavelet spectrum, FFT, and MTM spectral results from the clipped LITH scale (grayed part clipped off) of the upper part of the Haojiagou Formation
through the upper member of the Badaowan Formation in the Haojiagou section. Conventions for temporal information are as in Fig. S3. In the evolutive FFT,
white is the highest relative power and black is the lowest. In the FFT spectra, high-amplitude peaks are labeled with their periods in meters and ky (kiloyears)
assuming recognition of the 405-ky cycle. In the MTM spectra, only those peaks in spectral power that have f-test significance above the 0.9 level and high
amplitude are labeled, and they are labeled in meters and kiloyears based on recognition of the 405-ky level.
Sha et al. www.pnas.org/cgi/content/short/1501137112
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34.5m/405.0ky 8.8m/102.8ky 3.8m/44.6ky
7.7m/90.5ky
2.1m/24.9ky
2.0m/23.1ky
14000
700
600
12000
MTM
Relative Power Low Lith Index
f-test
400
8000
1.0
6000
300
200
400
0.5
200
100
0
0
A
B
C
D
Blackman-Tukey
140
coherency
0.9
0.8
0.7
0.6
0.5
0.4
120
100
80
60
2500
2000
1500
1000
40
500
20
0
3000
Relative Power High Lith Index
10000
500
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
1.0
0.9
0
Cycles / Meter
Fig. S5. Comparison of spectral analysis for the low LITH Index values (black in Figs. S3 and S4) and the high Index values (gray in Figs. S3 and S4) using the
multitaper method (MTM) with the f-statistic and the Blackman–Tukey method with coherence for the interval 435–690 m. The bands corresponding to orbital
frequencies are show in gray and are as follows: (A) 405-ky eccentricity (40.0–27.8 m) 469.6–326.4 ky; (B) ∼100-ky eccentricity (9.7–7.0m), 114.0–82.7 ky;
(C) obliquity (4.3–3.6 m), 50.6–41.6 ky; and (D) climatic precession (2.3–1.9 m), 26.6–22.5 ky. They are also labeled with the major specific picks from Fig. S4. Note
that the two methods give essentially the same results on the two sets of values from the LITH index, with the orbital period being highly significant (f > 0.9),
high relative spectral power, and coherence (>0.6).
AM Filtered ~40 ky cycles (3.6 m)
5
0
-5
350
400
450
500
Spectral Power Filtered
819 ky cycle (70 m)
A
550
600
650
700
750
Stratigraphic Depth
819 ky (70 m)
300
800
~1.6 m.y. (~143 m)
600
200
coherency
400
100
200
0
0
B
0.01
0.02
0
0.03
Spectral Power
AM Filtered ~40 ky
Cycles (3.6 m)
Filtered LITH Index
filtered 819 ky cycle (70 m)
10
Frequency (Cycles/m)
Fig. S6. Modulation of the lithological expression of ∼40-ky (3.6-m) obliquity cycle by the ∼819-ky (∼70-m) cycle identified by spectral analysis (Fig. S4).
(A) Comparison of AM filtered (Hilbert transform) of the filtered ∼40-ky cycle from the clipped LITH series, with the filtered ∼819-ky (∼70-m) cycle from the clipped
LITH series. Note the close correspondence between the two independent filtered series showing that the lithological expression of ∼40-ky (3.6-m) obliquity
cycle is in fact modulated by the ∼819-ky (∼70-m) cycle. (B) Blackman–Tukey spectra and coherence of the two series in A, showing quantitatively that the
lithological expression of ∼40-ky (3.6-m) obliquity cycle is coherent (above 0.7) with the filtered ∼819-ky (∼70-m) cycle. Note that some modulation by the 2 ×
819-ky cycle is expected within the obliquity band. The clipped LITH index series was bandpass filtered by frequency of 0.275 cycles/m (3.6-m period) with
a bandwidth of 0.02 and a Gaussian shape. The resulting series was AM filtered (Hilbert transform). The same clipped LITH index series was bandpass filtered at
a frequency of 0.014285 cycles/m (70-m period) with a bandwidth of 0.005 and Gaussian shape. Blackman–Tukey spectra were obtained with Analyseries
using a Bartlett window, with a bandwidth of 0.00416551, and the nonzero coherence is higher than 0.6056.
Sha et al. www.pnas.org/cgi/content/short/1501137112
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Lower Badoawan Depth (m)
480
500
520
540
560
580
600
620
640
0
LITH Index
20
40
60
80
100
120
140
405 ky
Fig. S7.
~100 ky
~40 ky
~20 ky
The various major cycles discussed in this paper as they appear in the LITH index.
Table S1. LITH index values (rock colors range from black to light gray)
Lithology
Coal or coal seam
Shale, carbonaceous shale
Mudstone
Silty mudstone
Muddy siltstone
Fine-grained siltstone
Medium-grained siltstone
Coarse-grained siltstone
Fine-grained sandstone
Fine-grained sandstone
Medium-grained sandstone
Coarse-grained sandstone
Fine conglomerate: ≤4-cm clasts
Medium conglomerate: ≤8-cm clasts
Coarse conglomerate: >8-cm clasts
Environment
LITH value
Dysoxic sediment-starved lake or swamp
Dysoxic lake
Shallow lake
Shallow lake
Shallow lake or paleosol
Shallow lake or paleosol
Floodplain or paleosol
Floodplain or paleosol
Floodplain and fluvial
Fluvial
Fluvial
Fluvial
Fluvial
Fluvial
Fluvial
10
25
30
40
50
55
60
65
70
80
90
100
110
120
130
Table S2. U-Pb and astrochronological ages compared: Explanation
Horizon or unit
Hettangian–Sinemurian boundary
Hook Mountain Basalt
Preakness Basalt
Rhaetian–Hettangian boundary
Orange Mountain Basalt
End–Triassic extinction
Newark igneous U-Pb
Not applicable
200.916 ± 0.064§
201.274 ± 0.032{
Not applicable
201.520 ± 0.034jj
201.564 ± 0.015††
Newark–Hartford APTS
Pucara Basin U-Pb
Bristol Channel Basin
Pucara*/Newark†
±
±
±
±
±
±
199.46 ± 0.17‡
Not applicable
Not applicable
201.36 ± 0.14#
Not applicable
201.51 ± 0.15
199.61/199.66
Not applicable
Not applicable
201.32/201.37
Not applicable
201.51/201.56
199.70
200.93
201.28
201.42
201.52
201.56
0.02
0.02
0.02
0.02
0.02**
0.02‡‡
*Using the Pucara ash-based ETE as a tie point (35).
†
Using the Newark igneous-based ETE as a tie point (30).
‡
Zircon 206Pb/238U age of Pucara Basin ash LM4-19B at the Hettangian–Sinemurian boundary, originally published as 199.43 ± 0.1 Ma (15) but adjusted here to
199.46 ± 0.17 based on a regression of ages of ashes dated by both Guex et al. (36) and Wotzlaw et al. (35), the latter using updated EARTHTIME protocols
(www.earth-time.org). B. Schoene (pers. comm., 02/15) has recalculated this age using current EarthTime protocols as 199.51 ± 0.10.
§
Zircon 206Pb/238U age of the Butner Diabase that applies to the Hook Mountain Basalt (30).
{
Zircon 206Pb/238U age of flow 2 of the Preakness Basalt (30).
#
Average age and rms error of marine Pucara Basin ashes LM4-100/101 and LM4-90 zircon 206Pb/238U ages that bracket the ammonite-calibrated Triassic–
Jurassic boundary (35).
jj
Zircon 206Pb/238U age of the Palisade Sill that applies to the Orange Mountain Basalt (30).
**Age of the Triassic–Jurassic boundary as projected into the Newark APTS (31).
††
Age of the continental ETE in the basins of Eastern North America and Morocco derived from zircon 206Pb/238U dates and astrochronology (30).
‡‡
Rounded age of the continental ETE (30) used as a tie point for the Newark astrochronology.
Sha et al. www.pnas.org/cgi/content/short/1501137112
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