TY - JOUR
T1 - Influence of vegetation type and site-to-site variability on soil carbonate clumped isotope records, Andean piedmont of Central Argentina (32-34°S)
AU - Ringham, Mallory C.
AU - Hoke, Gregory D.
AU - Huntington, Katharine W.
AU - Aranibar, Julieta N.
N1 - Funding Information:
We thank Almendra Brasca and Villavicencio, Divisadero Largo, and Nacuñan Nature Reserve park rangers for generous field assistance, and Andy Schauer and Kyle Samek for lab assistance at the University of Washington Isolab. This work was funded by a National Science Foundation grant 1251966 awarded to GDH, and grants 1252064 and 1156134 awarded to KWH. We thank our reviewers and editor for their constructive reviews.
Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2016/4/15
Y1 - 2016/4/15
N2 - The clumped isotope geothermometer estimates the formation temperature (T(Δ47)) of carbonates and has great potential to enhance the extraction of environmental data from pedogenic (soil) carbonate in the geologic record. However, the influence of vegetation type and site-specific conditions on carbonate formation processes and T(Δ47) records remains poorly understood. This study examines the potential for variability in T(Δ47) data between nearby, same elevation sites with different C3/C4 biomass. Pedogenic carbonates (undercoatings and nodules) were collected from five modern soil pits in the semi-arid eastern Andean piedmont of Argentina under a summer precipitation regime. Three pits were instrumented with temperature and moisture sensors to 1 m depth, and a fourth was instrumented with additional soil CO2 and atmospheric (temperature, relative humidity, insolation, and rainfall) sensors. T(Δ47) values (mean: 30±6°C (±1SE)) are invariant with depth and are statistically indistinguishable between the four instrumented sites, though a 10 °C difference between our T(Δ47) values and those of a nearby Peters et al. (2013, EPSL) study suggests the potential for significant site-to-site variability, likely due to local soil hydrology. The results of this study suggest that deeper (≥40 cm) T(Δ47) values are consistent with carbonate formation during the early part of soil drying immediately after large mid-summer rainstorms. Carbonate formation ≤ 40 cm depth may be biased to soil drying after small, frequent precipitation events occurring throughout the spring, summer, and fall months, averaging to shallow summer T(Δ47) values and resulting in a near-isothermal T(Δ47) profile.
AB - The clumped isotope geothermometer estimates the formation temperature (T(Δ47)) of carbonates and has great potential to enhance the extraction of environmental data from pedogenic (soil) carbonate in the geologic record. However, the influence of vegetation type and site-specific conditions on carbonate formation processes and T(Δ47) records remains poorly understood. This study examines the potential for variability in T(Δ47) data between nearby, same elevation sites with different C3/C4 biomass. Pedogenic carbonates (undercoatings and nodules) were collected from five modern soil pits in the semi-arid eastern Andean piedmont of Argentina under a summer precipitation regime. Three pits were instrumented with temperature and moisture sensors to 1 m depth, and a fourth was instrumented with additional soil CO2 and atmospheric (temperature, relative humidity, insolation, and rainfall) sensors. T(Δ47) values (mean: 30±6°C (±1SE)) are invariant with depth and are statistically indistinguishable between the four instrumented sites, though a 10 °C difference between our T(Δ47) values and those of a nearby Peters et al. (2013, EPSL) study suggests the potential for significant site-to-site variability, likely due to local soil hydrology. The results of this study suggest that deeper (≥40 cm) T(Δ47) values are consistent with carbonate formation during the early part of soil drying immediately after large mid-summer rainstorms. Carbonate formation ≤ 40 cm depth may be biased to soil drying after small, frequent precipitation events occurring throughout the spring, summer, and fall months, averaging to shallow summer T(Δ47) values and resulting in a near-isothermal T(Δ47) profile.
KW - Central Andean piedmont
KW - Clumped isotope thermometry
KW - Paleoclimate
KW - Pedogenic carbonate
KW - Stable isotopes
KW - Temperature proxy
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U2 - 10.1016/j.epsl.2016.02.003
DO - 10.1016/j.epsl.2016.02.003
M3 - Article
AN - SCOPUS:84957803857
SN - 0012-821X
VL - 440
SP - 1
EP - 11
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -