Sierra Nevada Speleothems:
Potential as high-resolution
archives of atmospheric
circulation over western North
America
Jessica Oster, Isabel Montañez,
Warren Sharp
42ºN
Precipitation
Black Chasm Cavern
32ºN
California Caverns
Sierra Nevada speleothems have
recorded changes in mid-latitude
atmospheric circulation over the late
Pleistocene and Holocene, including
changes in the mean position of the polar
jet stream over western North America.
ENSO and PDO signals will be present
in Sierra Nevada speleothems
Variations should be represented as
changes in the amount of precipitation
and degree of groundwater interactions
with soils and bedrock above Sierra
Nevada caves
Helictites and soda straws, Black Chasm
Monitor modern cave
environment
Develop dated geochemical
(Sr, Mg) and isotopic (δ18O,
δ13C, 87Sr/86Sr, 14C) proxy
records.
Compare with other Sierra
records, records from east
Pacific.
Modern Cave Environment
Rainwater
Soil Water
O,C,H, and Sr
isotopes
Ca, Sr, Mg conc.
Drip rate
Drip Water
Cave Air Temp,
humidity, pCO2
Sampling Strategy
Core sampling
Stalagmite Sampling
14cm
3D reconstructions
Core Samples
Entire
Stalagmites
Summer
2007
5.735 ± 38
9.830 ± 130
8.684 ± 0.199
Moaning Cave
9.845 ± 114
10.586 ± 93
12.391 ± 0.571
11.554 ± 164
13.217 ± 78
16.694 ± 366
17.285 ±0.666
17.020 ± 397
U-series
(calendar kyr)
14C
(calendar kyr)
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Decreased
growth rate
U-series vs. Radiocarbon
age models
Enhanced dead
carbon contribution
U-series - cal yrs
14C
- not calibrated
MC3 Hendy Tests
Hendy Tests
-10
Growth
bandR2 = 0.7649
-9.5
-9
Growth
R2 = 0.2884
axis
-8.5
-8
R2 =
R2 = 0.7663
-7.5
-7
-6.5
-6.5
-7
-7.5
-8
-8.5
δ18O
-9
-9.5
-10
δ18O
Years BP
8684 ± 199
12391 ± 571
Coincident with Younger Dryas
17285±0.666
‰
Moaning Cave
δ18O
δ13C
‰
Mg ppm
Sr ppm
Years BP
δ13C
δ18O
Moaning Cave Strontium Record
2σ
Host rock
87Sr/86Sr
Cave Waters
Speleothems
Soil leachates
Wetter?
more soil
input
Drier?
δ18O
δ13C
more marble
input
‰
Black Chasm Hendy Test
-10.90
Black Chasm Stalagmite
-10.95
-11.00
-11.05
2
R = 0.6703
δ13C
-11.10
-11.15
-11.20
-11.25
-11.30
-11.35
-11.40
-9.35
-9.30
-9.25
-9.20
δ18O
-9.15
-9.10
-9.05
-9.00
Moaning Cave
-5.00
-6.00
-7.00
δ13C
-8.00
-9.00
RR22 =
= 0.8046
-10.00
Black Chasm
-11.00
-9.50
-9.00
-8.50
-8.00
-7.50
-7.00
-6.50
-6.00
-6.00
δ18O
-7.00
δ13C
-12.00
-10.00
-5.00
2 =
2
RR
=
0.1814
-8.00
-9.00
-10.00
-11.00
-9.20
-9.10
-9.00
-8.90
-8.80
-8.70
-8.60
δ18O
-8.50
-8.40
-8.30
-8.20
-8.10
In Conclusion…
• Sierra Nevada speleothems are datable by Useries methods.
• Comparison of δ18O, δ13C, trace elements,
and 87Sr/86Sr indicate Sierra Nevada caves
record known climatic events.
• Future directions of research:
– Expand and compare proxy records for all caves
– Monitor cave environments in order to “ground
truth” proxy records.