www.sciencemag.org/cgi/content/full/319/5868/1377/DC1
Supporting Online Material for
Age and Evolution of Grand Canyon Revealed by U-Pb Dating of Water Table–
Type Speleothems
Victor Polyak,* Carol Hill, Yemane Asmerom
*To whom correspondence should be addressed. E-mail: [email protected]
Published 7 March 2008, Science 319, 1377 (2008)
DOI: 10.1126/science.1151248
This PDF file includes:
Materials and Methods
Figs. S1 to S4
Table S1
References
Supporting Online Material
www.sciencemag.org/cgi/content/full/xxxxxxx
Cave and Speleothem Descriptions
Materials and Methods
Figures S1, S2, S3
Table S1
Supplementary References
Cave and Speleothem Descriptions
Grand Canyon contains hundreds of caves, most of which are developed in the
Redwall or Muav limestones. These caves are of two basic types: vadose (unconfinedaquifer) caves and phreatic (confined-aquifer) caves (S1). The vadose caves are forming
today from water descending the Kaibab Plateau and discharging at places such as
Roaring Springs on the North Rim. The phreatic caves formed under artesian conditions
and contain speleothems which were deposited before, during, and after canyon incision
and which record the descent of the water table over time.
The sequence of speleothems (cave formations) in Grand Canyon caves that
relate to the position of the water table are spar crystals lining cave walls, mammillary
coatings overlying spar, gypsum rinds overlying mammillaries, and subaerial
speleothems such as stalactites, stalagmites, and coralloids overlying all of these. Not all
of these speleothem types are present in every cave, but the relative sequence of
deposits is always the same. The dissolution of cave passages takes place where the
solubility of calcium carbonate is at its maximum, probably at considerable depth (250550 m below the water table) (Fig. S1)(S2). Crystal spar linings form in the deeper
phreatic zone where the diffusion of CO2 is slow, while mammillaries form just below the
water table where the loss of CO2 is much faster. Gypsum rinds form just above the
water table where diffusing H2S forms sulfuric acid, which reacts with the limestone to
form replacement gypsum. And speleothems such as stalactites, stalagmites and
coralloids form above the water table in the air-filled zone. Figure S1A shows the
sequence of a spar lining, overlain by a mammillary coating, overlain by coralloids, which
sequence represents the phreatic, water-table, and subaerial episodes in the cave.
Figure S1B shows a mammillary overlain by a gypsum rind (partly pulled away from the
mammillary), which sequence again represents the lowering of the water table through
the cave.
1
The samples from site 6 (Gavain Abyss) and 8 (Bedrock Canyon) were surfaceexposed cave mammillaries, while all others were collected from caves. Samples from
site 2 (Dry Canyon) and 7 (Butte Fault Cave) were collected from very small caves.
Samples from sites 1 (Grand Canyon Caverns), 4 (Bobcat Cave, Grand Wash Cliffs,
near but not in the Grand Wash fault), 5 (Tsean Bida), and 9 (Shinumo Creek cave)
were considered text-book mammillaries from cave dark zones. White, fluid inclusion
rich areas in the samples were avoided. Densely crystalline (no visible porosity),
yellowish orange calcite was sampled in all cases. Subsamples were analyzed for U/Pb
ratios using ICPMS and those subsamples having high U/Pb ratios were selected for UPb dating.
Materials and Methods
Samples were crushed and collected in clean vials. Subsamples of these vials
consisted of individual pieces (0.02 to 0.2 g) that were etched in weak (<1 M) acid for 1015 seconds, washed in 18 MΩ H2O, dried, weighed, dissolved in 15N HNO3, spiked with
205
Pb, fluxed (1-2 hrs), dried, dissolved in aqua regia, dried, dissolved in 6N HCl, dried,
dissolved in 2N HCl, dried, dissolved in 1N HBr, and cleaned and separated with anion
resin in Teflon columns. Except for site 9 sample, all sample Pb and U ratios were
measured with a GV Sector 54 TIMS. Several U ratios and site 9 Pb ratios were
measured with a Neptune MC-ICMPS. Raw data was reduced using the PBDAT
computer program (S3). All appropriate ratios were corrected for excess 206Pb from
excess initial 234U, deficient 206Pb from lack of initial 230Th that was also corrected for
232
Th concentrations, and deficient 207Pb from lack of initial 231Pa (Fig. S2). U-Pb ages
were generated using the ISOPLOT computer program (S4) using our procedural Pb
blank of 30±8 (n=12) pg.
Ages are reported as 238U/204Pb, 235U/207Pb isochron dates and/or U-Pb
concordia-linear dates. A common-Pb 206Pb/204Pb value of 20.1 ± 2 % that is measured
in most of our 238U/204Pb isochrons was also used to determine initial 234U/238U values in
most samples. This high common-Pb value is consistent with values measured in Uores throughout Grand Canyon (S5). Younger mammillary samples (<2.5 Ma) with δ234U
values greater than 0 ‰ have calculated initial δ234U values of 3800 to 8000‰ (with the
exception of site 8, Bedrock Canyon mammillary = 520 ‰). These high values match
the measured value for spring water collected at Vasey’s Paradise (δ234U = 3130 ± 30
and 3120 ± 30 ‰, September 2004 and September 2006, respectively). For samples
2
>2.5 Ma old, an initial δ234U value of 3100 ‰ was used to adjust 238U/204Pb and 3-D
concordia dates. Figure S2 illustrates how initial 234U/238U values were determined. In
addition to Vasey’s Paradise water, high initial 234U/238U activities were also reported in
opal deposits near Yucca Mountain (δ234U up to and exceeding 5000 ‰), S6 only ~300
km west of Grand Canyon. Figure S4 graphically shows results of the other six isochron
dates.
We calculated slightly varying initial δ234U values in subsamples of two samples
(Table S1). We interpret this as a result of inexact layer sampling due to relatively slow
growth rate. Sample layers selected for analyses were somewhat thick to insure that
sufficient quantities of calcite were collected for analyses. These pieces were broken
into numerous smaller pieces to prevent contamination from saw blades. While all
pieces were from the same sampled layer, that layer was thick enough to represent
hundreds and perhaps even a few thousand years of calcite growth, explaining why
initial δ234U values could vary.
S1. P. W. Huntoon, Environmental and Engineering Geoscience 6 (2) 155 (2000).
S2. Y. V. Dublyansky, in, Speleogenesis: Evolution of karst aquifers, A.B., Klimchouk,
D. C. Ford, A. N. Palmer, W. Dreybrodt, eds. National Speleological Society,
Huntsville, Alabama, pp. 158-159 (2000).
S3. K. R. Ludwig, USGS Open-file Report 88-542, 30 pages (1993).
S4. K. R. Ludwig, Berkeley Geochronology Center Special Publication No. 1a, Berkeley
(2001).
S5. K. R. Ludwig and K. R. Simmons, Econ. Geol. 87, 1747 (1992).
S6. L. A. Neymark, Y. V. Amelin, J. B. Paces, Geochim. Cosmochim. Acta 64, 2913
(2000).
S7. H. Cheng, R. L. Edwards, J. Hoff, C. Gallup, D. A. Richards, Y. Asmerom, Chem.
Geol. 169, 17 (2000).
S8. R. L. Edwards, H. Cheng, M. T. Murrell, S. J. Goldstein, Science 276, 782 (1997).
3
A
Coralloids form on top of
the mammillaries above
the water table.
Mammillary calcite (M) and overlying
gypsum rind (G) separated from the
wall in site #1 cave.
Cave mammillaries
form below but very
near the water table.
M
Spar linings form well
below the water table.
B
2 cm
Solubility of CaCO3, g/L
2
1
gypsum rinds just a
few meters above
the water table
0
Canyons expose caves
and allow formation of
dripstones and
flowstones well above
water table.
10 cm
Mammillary coatings form at the
water table at the interface
between the phreatic and vadose
zones by outgassing of CO2 from
ground waters. This graph is for a
hydrothermal system (perhaps 3-4
times higher geothermal gradient
than Grand Canyon region) but in
general it shows the conditions
necessary for formation of cave
passages, calcite spar, and
mammillaries (modified from
Dublyansky, (S2)).
Dissolution of cave passages
(maximum solubility at 250-550 m)
C
Spar lining formation
mammillary
formation very
near water table
225ºC
25ºC
0
folia and cave rafts
at the water table
2
1
Depth, km below water table
Gypsum rinds develop
above water table while
water table present in
cave. Folia and cave
rafts form at water table.
G
3
Growth of mammillary
Spar linings (calcite)
coatings takes place below forms well below the
and near the water table.
water table.
Cave
le
r t ab
e
t
a
W
D
CO2 & H2S migrate
upward into caves
along joints
Spar lining
Cave mammillary
Gypsum rind
Water table
Dripstones (stalactites, stalagmites, coralloids)
Figure S1. (A) Image of cave mammillary sample showing yellowish orange mammillary calcite;
(B) cave occurrence of exceptionally well-formed mammillary coating and overlying gypsum rind;
(C) conceptual graph illustrating sequence of cave deposition; and (D) a sketch illustrating the
theorized progression of speleothem deposition related to position of groundwater table.
U-Pb model age corrected for excess 206Pb from δ234Ui (206Pb/204Pbi=20)
4.E+06
U-Pb model age corrected for
δ234Ui (206Pb/204Pbi=19)
3.E+06
2.2 Ma (mammillary age)
Age
(yrs) 2.E+06
Tδ234U = ln[δ234Ui/δ234Um-1]/λ234
δ234U age (δ234Um = 12 ‰)
1.E+06
7000
0.E+00
0
2000
4000
6000
8000
δ234Uinitial
10000
12000
14000
16000
(‰)
Figure S2. Graphical representation of method for correction of excess and deficient initial 206Pb
regarding initial 234U/238U (δ234Umeas > 0‰), initial 230Th/238U, and initial 231Pa/235U. Calculated subsample
model ages for the Dry Canyon mammillary from site 3, used the equation below, where λ238 = 1.55125E10, λ235 = 9.84850E-10, λ234 = 2.8263E-6, λ231 = 2.1158E-5, λ230 = 9.1577E-6 (S7, S8). The subscripts in
the equations below are * = radiogenic ratio, m = measured, i = initial, u = from excess 234U, th = from
deficient initial 230Th, and pa = from deficient initial 231Pa. When considering a lower 206Pb/204Pbi = 19, the
corrected model age only increases slightly to about 2.2 Ma showing that the system is not greatly
sensitive to 206Pb/204Pbinitial.
Equations used for corrections
206
Pb*
=
204
Pb
206
Pb
204
Pbm
206
238
Pb
U
=
(
)
204
204
Pbu
Pb
206
Pb
=
204
Pbth
207
Pb
204
Pb*
207
=
Pb
=
204
Pbpa
238
U
206
Pb
204
Pbi
207
Pb
204
Pbm
235
+
U
206
Pb
204
Pbth
λ
Ui
) ( λ238 )
1000
234
230
λ238
Th 232Th
( λ ) - (232 )( 238 )
Thi
U
230
234
]
207
Pb
204
Pbpa
( 204Pb ) [(
*
Pb
+
204
Pbu
(δ
( 204Pb ) [
*
206
231
λ235
Pa 232Th
-(
)(
)
)
232
λ231
Thi 235U
]
Shivwits Plateau
Elevation (m)
1800
1500
Supai
1200
Site 4
Site 1
Redwall
900
Site 2
Site 3
Muav
600
Colorado River
115 km
A
B
Kaibab Plateau
Elevation (m)
2400
Coconino Plateau
2000
Supai
1600
Redwall
Muav
Site 5
Site 6
1200
Colorado River
800
37 km
C
D
Incision rate (m/My)
600
500
Mammillary formed at water table
Mammillary formed 100 m below water table
400
Mammillary formed 100 m above water table
300
200
100
0
0
50
100
150
River-mile
200
250
300
Figure S3. (A) Cross-section from A to B on Figure 2 showing the general pertinent stratigraphy,
approximate cave locations within that stratigraphy, and area relief on the western end of Grand Canyon.
The dashed line represents approximate elevation for the top of the Hualapai Limestone. (B) Crosssection from C to D on figure 2 represents the eastern end of Grand Canyon. (C) Incision rates versus
river-mile locations. In this graph, results are offered for a scenario where the cave mammillaries formed
100 m below the water table, and 100 m above the water table. Even with consideration of these
extremes, distinctly different incision histories stand out between the eastern and western Grand Canyon.
0.58
0.50
0.46
0.73
0.72
Age = 2.17 ± 0.34 Ma
MSWD = 0.92, probability =0.50
0.71
Common-Pb plane intercepts at
206Pb/204Pb = 20.03 ± 0.27
207Pb/204Pb = 15.878 ± 0.040
site 1
0.42
site 3
0.74
Pb/206Pb
207
Pb/206Pb
0.54
0.75
207
Age = 7.55 ± 0.34 Ma
MSWD = 0.29, probability =0.98
Common-Pb plane intercepts at
206Pb/204Pb = 21.07 ± 0.57
207Pb/204Pb = 15.815 ± 0.080
0.70
0.38
220
260
300
340
380
170
420
190
210
238
U/206Pb
230
238
U/
250
206
270
290
Pb
0.75
Age = 16.96 ± 0.83 Ma
MSWD = 7.5, probability =0.000
Common-Pb plane intercepts at
206Pb/204Pb = 20.121 ± 0.033
207Pb/204Pb = 15.761 ± 0.021
0.71
Pb/
206
0.775
0.73
0.765
207
207
Pb/206Pb
0.785
Pb
0.795
0.755
0.67
Age = 2.19 ± 0.47 Ma
MSWD = 1.6, probability =0.12
Common-Pb plane intercepts at
206Pb/204Pb = 19.89 ± 0.49
207Pb/204Pb = 15.72 ± 0.10
0.65
site 4
0.745
site 5
0.69
0.63
0.61
0.735
1
3
5
7
9
238
206
U/
11
13
15
150
17
250
350
450
238
Pb
U/
206
550
650
Pb
0.82
Age = 2.68 ± 0.49 Ma
MSWD = 0.53, probability =0.86
Common-Pb plane intercepts at
206Pb/204Pb = 19.00 ± 0.36
207Pb/204Pb = 15.814 ± 0.061
Pb/206Pb
0.7
0.78
207
0.76
0.74
0.5
0.4
site 8
0.3
site 7
0.72
120
0.6
160
200
0.2
240
0
280
1000
2000
3000
238
238
U/206Pb
206
4000
5000
6000
Pb
Age = 3.72 ± 0.80 Ma
MSWD = 8.8, probability =0.000
Common-Pb plane intercepts at
206Pb/204Pb = 19.18 ± 0.97
207Pb/204Pb = 15.78 ± 0.29
0.72
Pb/206Pb
U/
0.68
0.64
207
207
Pb/206Pb
0.80
Age = 0.828 ± 0.046 Ma
MSWD = 0.86, probability =0.51
Common-Pb plane intercepts at
206Pb/204Pb = 19.97 ± 0.48
207Pb/204Pb = 15.99 ± 0.39
0.8
0.60
site 9
0.56
150
250
350
238
U/
450
206
550
Pb
Figure S4. 3-D linear-constrained concordia isochron ages for sites 1, 3, 4, 5, 7, 8, & 9.
Table S1. U-Pb data.
Pb (ppb)
δ234U
(‰)a
1
bob1-1
bob1-2
bob1-3
bob1-4
bob1-5
bob1-6
3.445
3.016
3.032
2.851
3.124
2.828
±
±
±
±
±
±
0.233
0.219
0.117
0.047
0.040
0.219
0.023
0.017
0.023
0.016
0.030
0.027
±
±
±
±
±
±
0.464
0.838
0.722
0.280
1.750
0.690
12.2
13.5
11.5
12.8
14.3
11.8
±
±
±
±
±
±
1.1
0.8
1.1
1.0
1.4
1.1
3100
3100
3100
3100
3100
3100
11946.0
14914.0
10632.0
15061.0
8107.2
8036.7
±
±
±
±
±
±
1.0
2.0
1.6
4.2
3.0
1.9
36.845
40.812
35.283
41.362
31.765
31.740
±
±
±
±
±
±
0.475
1.030
0.694
2.110
1.450
0.706
16.447
16.609
16.397
16.613
16.401
16.256
±
±
±
±
±
±
0.320
0.562
0.305
0.430
2.140
0.282
341.2
387.1
315.9
385.6
265.6
263.4
±
±
±
±
±
±
1.1
2.2
1.7
4.7
3.3
2.0
0.4698
0.4312
0.4873
0.4255
0.5374
0.5329
2
NBC5-1
NBC5-2
NBC5-3
NBC5-4
2.696
2.743
2.276
2.891
±
±
±
±
0.193
0.041
0.034
0.072
0.014
0.017
0.021
0.140
±
±
±
±
0.720
1.040
0.375
0.188
-0.7
3.1
2.5
2.7
±
±
±
±
1.5
1.0
0.8
0.9
3100
3100
3100
3100
14336.0
12323.0
7799.7
1394.8
±
±
±
±
1.4
2.0
0.7
0.3
31.167
29.698
26.504
21.578
±
±
±
±
0.514
0.667
0.196
0.118
16.172
16.120
16.018
15.795
±
±
±
±
0.295
0.418
0.181
0.166
494.8
443.1
308.2
65.3
±
±
±
±
0.7
1.0
0.4
0.2
0.5584
0.5798
0.6330
0.7393
3
Dry1
Dry2
Dry3
Dry4
Dry5
Dry6
0.995
1.105
1.642
1.388
1.133
1.143
±
±
±
±
±
±
0.244
0.202
0.126
0.154
0.090
0.079
0.013
0.014
0.015
0.022
0.014
0.013
±
±
±
±
±
±
1.560
0.652
0.763
0.970
2.880
2.000
12.2
13.5
11.5
12.8
14.3
11.8
±
±
±
±
±
±
1.1
0.8
1.1
1.0
1.4
1.1
5790
6795
4920
7010
5935
5900
5451.3
5375.9
5194.8
4282.0
5620.4
5967.1
±
±
±
±
±
±
2.6
1.1
2.6
1.6
4.9
3.4
23.533
23.740
23.042
23.057
23.595
23.946
±
±
±
±
±
±
0.481
0.244
1.300
0.290
0.892
0.627
15.932
15.963
15.713
15.927
15.981
15.981
±
±
±
±
±
±
0.289
0.204
1.450
0.459
0.278
0.278
249.0
246.3
239.1
199.3
257.1
269.8
±
±
±
±
±
±
2.6
1.1
2.9
1.6
4.9
3.4
0.7278
0.7315
0.7233
0.7415
0.7312
0.7227
4
GCC-p1
GCC-p2
GCC-p3
GCC-p4
GCC-u1
GCC-u2
GCC-u3
5.488
5.134
4.682
8.414
8.264
8.994
3.958
±
±
±
±
±
±
±
0.264
1.450
0.314
0.204
0.383
0.109
0.093
2.789
3.110
3.102
1.943
2.141
2.036
3.239
±
±
±
±
±
±
±
0.193
0.108
0.127
0.087
0.171
0.110
0.136
2.3
4.4
0.4
-0.6
-1.8
3.0
0.0
±
±
±
±
±
±
±
2.9
4.0
3.8
3.6
4.2
4.4
3.1
3100
3100
3100
3100
3100
3100
3100
130.9
119.1
100.5
81.2
290.9
259.3
297.1
±
±
±
±
±
±
±
0.3
0.6
0.4
0.2
0.3
0.4
0.3
20.492
20.412
20.415
20.349
20.928
20.850
20.975
±
±
±
±
±
±
±
0.120
0.105
0.101
0.104
0.148
0.069
0.255
15.759
15.761
15.780
15.774
15.791
15.810
15.813
±
±
±
±
±
±
±
0.164
0.154
0.151
0.153
0.186
0.096
0.191
6.4
5.8
4.9
4.0
13.9
12.5
14.2
±
±
±
±
±
±
±
0.3
0.6
0.3
0.2
0.2
0.4
0.2
5
GAM1*
GAM2
GAM3
GAM4
GAM5
GAM6
0.918
1.046
0.850
0.851
0.871
1.012
±
±
±
±
±
±
0.046
0.051
0.051
0.899
0.052
0.048
0.008
0.007
0.009
0.009
0.010
0.005
±
±
±
±
±
±
0.850
3.350
1.540
0.994
1.620
4.220
9.9 ± 0.6
8.2 ± 0.8
12.0 ± 1.1
8.4 ± 28.6
8.6 ± 0.9
6.3 ± 1.0
5160
3605
2660
2750
3920
4360
6822.2
9927.0
6304.4
6822.2
5849.1
13744.0
±
±
±
±
±
±
1.8
5.9
2.5
1.4
2.7
8.1
23.082
25.112
22.686
23.082
23.129
27.985
±
±
±
±
±
±
0.283
1.260
0.774
0.402
0.461
2.210
15.984
16.032
15.643
15.818
15.841
16.084
±
±
±
±
±
±
0.322
0.477
0.820
0.194
0.266
0.551
320.8
425.8
288.2
307.8
266.2
551.3
±
±
±
±
±
±
6
upb-1
upb-2
upb-3
upb-4
upb-5
7b-1
7b-2
7b-3
7b-4
7b-5
upb-6
upb-7
2.170
3.828
2.115
2.170
2.115
2.380
1.646
2.337
2.264
2.281
3.155
1.366
+/- 0.153
+/- 0.136
+/- 0.153
+/- 0.153
+/- 0.153
± 2.420
± 0.000
± 0.860
± 0.708
± 0.362
± 0.144
± 1.470
0.676
1.004
0.537
0.787
0.532
0.293
0.271
0.167
0.197
0.437
0.806
0.322
+/- 0.93
+/- 0.131
+/- 2.2
+/- 0.149
+/- 0.149
± 0.121
± 1.590
± 0.218
± 0.234
± 0.124
± 0.088
± 0.109
-1.5 ± 2.2
-0.1 ± 2.5
0.6 ± 2.9
0.2 ± 3.3
-1.2 ± 3.3
8.8 ± 3.3
3.5 ± 4.2
15.7 ± 72.4
0.5 ± 4.1
-3.3 ± 8.0
4.3 ± 12.7
-3.5 ± 6.7
3100
3100
3100
3100
3100
3100
3100
3100
3100
3100
3100
3100
214.4
254.5
265.9
185.5
298.0
544.3
563.5
940.5
775.7
349.3
261.5
283.3
±
±
±
±
±
±
±
±
±
±
±
±
1.0
0.2
0.2
1.9
1.0
2.6
1.7
0.9
0.8
0.4
1.9
0.2
20.168
20.171
20.185
20.120
20.161
20.368
20.316
20.613
20.567
20.232
20.160
20.148
±
±
±
±
±
±
±
±
±
±
±
±
0.233
0.149
0.102
0.224
0.105
0.208
0.591
0.182
0.207
0.163
0.262
0.104
15.794
15.765
15.794
15.766
15.766
15.805
15.749
15.749
15.816
15.853
15.853
15.785
±
±
±
±
±
±
±
±
±
±
±
±
0.259
0.207
0.151
0.253
0.195
0.239
0.605
0.605
0.231
0.267
0.267
0.199
10.6
12.6
13.2
9.2
14.8
26.8
27.9
46.0
38.0
17.3
13.0
14.1
butte1
butte2
butte3
butte4
butte5
butte6
0.675
0.744
0.744
0.640
0.665
0.658
±
±
±
±
±
±
0.075
0.089
0.088
0.063
0.060
0.085
0.010
0.009
0.006
0.014
0.014
0.010
±
±
±
±
±
±
2.220
2.160
2.160
1.620
0.000
3.980
6.9
4.9
3.8
8.2
6.3
8.0
±
±
±
±
±
±
1.2
1.7
1.5
1.8
1.7
1.3
5130
4360
4970
6000
5080
7850
4839.2
4755.5
5420.4
3055.7
3256.8
4665.0
±
±
±
±
±
±
3.6
2.3
3.5
3.2
2.8
6.6
22.238
22.029
22.719
21.261
21.250
22.894
±
±
±
±
±
±
0.523
0.362
0.537
1.950
0.966
1.030
15.890
15.926
15.909
15.850
15.807
15.894
±
±
±
±
±
±
0.318
0.287
0.267
1.960
0.983
0.752
gcbed1
gcbed2
gcbed3
gcbed4
2.300
1.752
1.980
2.190
±
±
±
±
0.151
0.172
0.117
0.057
0.004
0.006
0.001
0.001
±
±
±
±
1.400
3.590
9.750
4.100
47.3
47.7
49.7
49.2
±
±
±
±
7.2
2.2
1.2
1.1
525
525
525
525
42631.0 ± 12.8
18638.0 ± 5.8
93057.0 ± 13.0
226350.0 ± 12.7
25.589
22.860
32.681
52.254
±
±
±
±
3.350
2.750
4.620
7.480
16.178
16.221
16.477
17.112
±
±
±
±
bot3
bot4
bot5
bot6
bot7
bot8
1.162
1.166
1.066
1.100
1.160
1.174
±
±
±
±
±
±
0.188
0.050
0.079
0.102
0.032
0.052
0.009
0.014
0.006
0.006
0.011
0.008
±
±
±
±
±
±
1.630
1.690
3.280
1.810
1.400
2.010
-2.9
-1.8
-2.2
-1.4
0.7
2.9
±
±
±
±
±
±
1.1
1.3
1.3
1.3
0.8
0.8
3100
3100
3100
3100
3100
3100
25.433
23.220
27.988
27.714
24.989
27.864
±
±
±
±
±
±
0.694
0.471
2.280
1.290
0.673
1.120
15.979
15.887
15.825
15.691
15.716
15.950
±
±
±
±
±
±
subsite sample
7
8
9
U (ppb)
δ234U
(‰)b
238U/204Pb
9268.7
5640.1
12344.0
12159.0
7333.7
11332.0
±
±
±
±
±
±
2.9
2.8
6.4
3.4
2.4
3.7
206Pb/204Pb 207Pb/204Pb
238U/206Pb 207Pb/206Pb 204Pb/206Pb
c
c
c
±
±
±
±
±
±
0.5727
1.1733
0.7581
2.1534
2.5850
0.7602
0.0286
0.0260
0.0297
0.0256
0.0328
0.0328
±
±
±
±
±
±
0.4750
1.0300
0.6940
2.1100
1.4500
0.7060
0.449
0.605
0.163
0.064
0.0345
0.0360
0.0395
0.0468
±
±
±
±
0.5140
0.6670
0.1960
0.1180
±
±
±
±
±
±
0.5611
0.3180
1.9474
0.5429
0.3117
0.4434
0.0457
0.0458
0.0460
0.0466
0.0457
0.0452
±
±
±
±
±
±
0.4810
0.2440
1.3000
0.2900
0.8920
0.6270
0.7698
0.7728
0.7735
0.7756
0.7562
0.7597
0.7555
±
±
±
±
±
±
±
0.0503
0.0507
0.0501
0.0502
0.0507
0.0503
0.0529
0.0488
0.0490
0.0490
0.0492
0.0479
0.0481
0.0478
±
±
±
±
±
±
±
0.1200
0.1050
0.1010
0.1040
0.1480
0.0690
0.2550
1.9
6.0
2.7
1.5
2.7
8.4
0.7518
0.6877
0.7153
0.7137
0.7211
0.6454
±
±
±
±
±
±
0.4287
1.3473
1.1276
0.4464
0.5322
2.2777
0.0470
0.0429
0.0457
0.0451
0.0455
0.0401
±
±
±
±
±
±
0.2830
1.2600
0.7740
0.4020
0.4610
2.2100
±
±
±
±
±
±
±
±
±
±
±
±
1.1
0.3
0.3
1.9
1.0
2.6
1.8
0.9
0.8
0.4
1.9
0.2
0.7845
0.7833
0.7842
0.7848
0.7840
0.7795
0.7789
0.7700
0.7740
0.7859
0.7881
0.7853
±
±
±
±
±
±
±
±
±
±
±
±
0.3484
0.2550
0.1822
0.3379
0.2215
0.3168
0.8458
0.6318
0.3102
0.3128
0.3741
0.2245
0.0497
0.0497
0.0497
0.0498
0.0497
0.0493
0.0495
0.0489
0.0489
0.0496
0.0497
0.0498
±
±
±
±
±
±
±
±
±
±
±
±
0.2330
0.1490
0.1020
0.2240
0.1050
0.2080
0.5910
0.1820
0.2070
0.1630
0.2620
0.1040
230.9
226.8
254.1
150.5
159.7
222.5
±
±
±
±
±
±
3.6
2.4
3.6
3.7
2.9
6.7
0.7583
0.7595
0.7459
0.7806
0.7750
0.7583
±
±
±
±
±
±
0.6121
0.4620
0.5997
2.7648
1.3782
1.2753
0.0477
0.0477
0.0469
0.0492
0.0490
0.0477
±
±
±
±
±
±
0.5230
0.3620
0.5370
1.9500
0.9660
1.0300
1.070
3.280
1.430
1.820
1699.6
823.3
2947.1
4566.7
±
±
±
±
1.4
3.6
9.8
4.1
0.6456
0.7168
0.5230
0.3468
±
±
±
±
3.0000
1.9400
7.9500
6.3600
0.0399
0.0442
0.0317
0.0202
±
±
±
±
3.3500
2.7500
4.6200
7.4800
0.235
0.235
0.256
2.780
2.780
1.690
386.0
252.3
473.0
470.3
307.3
433.7
±
±
±
±
±
±
2.9
2.8
6.8
3.7
2.5
3.9
0.6656
0.7107
0.6066
0.6071
0.6586
0.6106
±
±
±
±
±
±
0.7327
0.5264
2.2943
3.0647
2.8603
2.0274
0.0416
0.0447
0.0383
0.0387
0.0419
0.0383
±
±
±
±
±
±
0.6940
0.4710
2.2800
1.2900
0.6730
1.1200
±
±
±
±
All errors are in % 2σ except for δ234U, which is absolute 2σ. Last three columns are ratios corrected for excess 206Pb from
decay of initial excess 234U. Site numbers correspond to site numbers in Table 1 and in the text. δ234Ua = measured value,
δ234Ub = calculated or assumed initial value. * - GAM1 data rejected for isochron plot.