Supplementary:
Figures:
Suppl. Fig. 1. The Shell Bar from the Qaidam Basin
Shell Bar is 2-3 m higher than the surrounding playa surface and stretches in a NWW-SEE direction for 2130 m, the widest
part being 140 m with a mean elevation of about 2700 m asl (varying between 2698 – 2702 m a.s.l.). A: the appearance of the
Shell Bar (36º 30´N, 96º 12´E) shows the surface disturbance by local people. We named it “Shell Bar” as it was characterized
by underwater formation features and by layers of shells of Corbicula and continuously distributed ostracods assemblages.
From a “Shell Ridge” to a Shell Bar” implies a concept transformation from a morphology description to original process; B:
our section (Zhang et al., 2007; 2008) with the author in the field; C: The photo of Shell Bar from delta-winged aircraft taken by
the author. There are two unique springs at the top of this elevated Shell Bar and we named them as Big Spring and Upper or
Top Spring individually (see Zhang et al, 2007; 2008, there were no names for these two springs before)
Suppl. Fig. 2. The color variations in layer 1 indicates reduction-oxidation processes induced by water level fluctuations
Suppl. Fig. 3. Shell Bar section and the features of each layer
Suppl. Fig. 4. Modern halite precipitation in Qarhan salt lake
(we use this photo to show a possible scenario how the salt layer covering the Shell Bar section was formed)
A-B
4000
SE
Kunlun Mts.
a
3600
3200
2800
0
100000
200000
300000
400000
500000
600000
2800
Average paleolake level
2750
altitude (m asl)
2700
b
2650
0
100000
200000
300000
400000
500000
distance (m)
4000
C-D
SW
Kunlun Mts.
3500
c
3000
2500
0
50000
100000
150000
200000
250000
2800
Estimated max.
paleolake level
2750
2700
Estimated min.
paleolake level
d
2650
0
20000
40000
60000
80000 100000 120000 140000 160000 180000
distance (m)
Suppl. Fig. 5. Topographical sections along A-B and C-D (see Fig. 1) based on SRTM data
(a: shows the flat low basin stretches in NWW–SEE direction for more than 500km, indicating weak/uniform tectonic activities
in the basin; b: enlarged topography shows the landform change in detail. c: N-S landscape changes modified by marginal
faults and alluvial/fluvial fans and d: enlarged landscape with the estimated Maximum and Minimum paleolake levels. It was
estimated the water level fluctuated between 2703 and 2710 (2715) m a.s.l. during the formation of the Shell Bar section, from
layer 8 to layer 1 in suppl. Fig. 2)
Suppl. Fig. 6. Sedimentation property and dating on the fossil shell of Corbicula and snails (kindly supplied by Jay Quade)
Suppl. Fig. 7. The relationship between the beach deposits (T21, T22 and T23) and section B20 on that Long and others
(2011) have dated using OSL technique (b). We have noticed this layer since when we found Baijianhu paleolake terraces
and we dug a section several meters in depth as described in our early paper.
Suppl. Fig. 8. The Shell Bar and surrounding landscapes
(a, the green arrow indicates the direction of modern seasonal rivers from the upper part of mega-fluvial fans that
perpendicular to the Shell Bar, this possibly resulted in the appearance of the two springs on the Shell Bar. It also clear that
seasonal rivers from southeast direction flow to the center of the basin in the direction of NW, while the Shell Bar stretches in
a SEE –NWW direction in general; the fat red and yellow arrows show the tail of the Shell Bar, such kind of shape is not easy
to be explained by a river or stream, the yellow lines mark the elevated linear sediments parallel to the shell bar. The
surrounding area of the Shell Bar is not deflation area even today. b, the shape of modern eroded channels, photo from
delta-winged aircraft taken by the author)
Suppl. Fig. 9. C-M graph of the grain size distribution from the Shell Bar section
(A C-M graph of Shell Bar section (our data came from 89 samples of a continuously sampling on the 2.6m thick section,
which is different from that by Mischke et al., 2014, they have displayed analyses results sampled at various points). In the
graph, the volume of C, that indicates the grain size at 1% of accumulation grain content and represents the maximum
transportation force, is less than 400m, while that of M, that indicates the grain size at 50% of accumulation grain content
and represents the average transportation force, is less than 200m. Grain size data of Shell Bar section shows that the C-M
relation of grain size can be divided into two groups, group 1 almost parallel to the C=M line and represents graded
suspension sediments, while group two represents traction current sediments that appear in typical lakes. We did not found
grains larger than 1000m transported by the river flow, and we think even Mischke and colleagues (2014) found a piece of
gravel it doesn’t mean the sediments should be “stream deposits”)
Suppl. Fig. 10. Landscape from mega-fluvial fan to the Shell Bar (red cross)
(1. Mega fluvial fan. 2. Farmland looks like picture A. 3. Erosion-deflation belt, picture B, showing the old lacustrine deposits
was taken from this belt and picture C took from the front of this belt, the cliff-like outcrops distributed along the red line
between 3 and 4. 4. The inner part of the basin. We believe the sediment cliff around paleolake at about 2710m elevation was
older than Shell Bar and was the formal backward erosion belt)
Suppl. Fig. 11. Comparison between the stratigraphy of the Shell Bar section by the author et al., Q. S. Fan, 2009 and Lai et
al., 2013. Note the differences between them. They just worked on the section we dug in 2003 (see Suppl. Fig. 1 and Fig. 2),
which still can be seen today. In the figure the black dots marked A-K in the section given by Fan in 2009 indicate the sample
points, black circle marked 2A and 2B were sampling points by Lai et al., 2014 for OSL dating. We have checked the
thickness of the salt layer in the Shell Bar and found generally it was around 10cm thick, therefore we are doubt about the
reliability of the stratigraphy descriptions by both Fan (2009) and Lai et al. (2014), apparently Fan did not recognize the
unconformity between layer 8 and layer 9 described in our publication, and we also wondered about why Lai and other had
put the disturbed salt layer in the section (also see Suppl. Fig. 1A and C for details).
Suppl. Table 1. OSL age of Shell Bar section given by Q. S. Fan, 2009 (Table 3, Fig. 5.5 and 5.9) and Lai et
al., 2014
number
Depth
(cm)
water
content
U/ppm
Th/ppm
K/%
(%)
Dose rate
De
OSL age
(Gy/ka)
(Gy)
(ka BP)
corrected
OSL age
(ka BP)
BQD1-K
60
1.0±5
1.22±0.22
5.57±0.38
1.67±0.05
2.61±0.12
305±14
117±5.3
76±5
BQD1-J
70
2.0±5
1.4±0.21
5.57±0.32
1.65±0.04
2.53±0.08
303±9
120±3.7
78±4
BQD1-I
120
4.0±5
1.47±0.20
5.7±0.28
1.47±0.04
2.38±0.15
325±20
137±8.4
89±8
BQD1-H
170
9.5±5
3.41±0.26
14±0.48
2.56±0.06
4.17±0.06
421±16
101±3.8
101±4
BQD1-G
190
9.5±5
3.09±0.30
10.9±0.41
2.08±0.05
3.46±0.09
381±10
110±3.0
110±3
BQD1-F
210
9.1±5
3.07±0.26
12.5±0.43
2.34±0.05
3.78±0.18
397±19
105±4.9
105±5
BQD1-E
265
4.7±5
2.73±0.25
10.6±0.40
1.92±0.05
3.19±0.11
373±13
117±3.9
117±4
BQD1-D
285
6.8±5
3.13±0.26
12.1±0.44
2.4±0.06
3.8±0.18
457±22
120±5.8
120±6
BQD1-C
320
10.1±5
2.41±0.23
10.2±0.39
1.98±0.05
3.13±0.08
420±10
134±3.2
134±3
BQD1-B
336
9.9±5
2.94±0.27
9.5±0.37
2.15±0.05
3.35±0.06
391±9
117±2.6
135±3
BQD1-A
372
10.4±5
2.83±0.25
121.5±0.44
2.3±0.05
3.58±0.11
384±8
107±2.3
143±2
2B
144
1.12±0.19
5.47±0.19
1.7±0.09
2.52±0.23
248±7
99±10
2A
178
1.41±0.12
6.09±0.19
1.65±0.06
2.58±0.22
290±10
113±10
Fan 2009 (the formal Ph.D student advised by Lai and Ma) corrected his OSL ages based on the discussion that he
believed OSL ages of C-H possess an almost linear depth-age correlation and were believable, so the OSL ages of
samples A and B were under estimated, while that of I, J and K were much over estimated, based on the linear
correlation he got the “corrected” OSL ages for these samples. 2A and 2B were dated by Lai et al (2013). Among
them, the sampling depth of 2B is equivalent to 59cm and 2A to 93cm in the section described by Fan (2009).
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