1. Geography and Environmental Science
Earthworm secreted calcite
granules as a
palaeoenvironmental proxy
Emma Versteegh, Stuart Black, Mark Hodson
15 September 2011 Frontiers in Environmental Geoscience www.reading.ac.uk

2. A new terrestrial
palaeoenvironment thermometer
• Many organisms
biomineralise
• Stable isotopes in
CaCO3 can record
environmental
variability
Earthworm secreted calcite granules as a palaeoenvironmental proxy 2

3. Earthworm secreted
calcite (CaCO3) granules
Earthworm secreted calcite granules as a palaeoenvironmental proxy 3

4. Aim
To construct a new terrestrial isotope – temperature curve
for application to earthworm secreted calcium
carbonate granules
→ Potential for granules in dating and palaeo-
environmental interpretation
Earthworm secreted calcite granules as a palaeoenvironmental proxy 4

5. Oxygen isotopes (δ18O values)
1000 ln αc-w = 18.03 (103T-1) - 32.42
δ18Owater & temperature → δ18Ocalcite
Kim & O’Neil (1997)
Earthworm secreted calcite granules as a palaeoenvironmental proxy 5

6. Earthworm secreted calcite granules as a palaeoenvironmental proxy 6

7. Earthworm secreted calcite granules as a palaeoenvironmental proxy 7

8. Earthworm secreted calcite granules as a palaeoenvironmental proxy 8

9. Earthworm secreted calcite granules as a palaeoenvironmental proxy 9

10. Aim
To construct a new terrestrial isotope – temperature curve
for application to earthworm secreted calcium
carbonate granules
• Potential for granules in dating and palaeo-
environmental interpretation
• How important are granules in locking up atmospheric
CO2?
Earthworm secreted calcite granules as a palaeoenvironmental proxy 10

11. Carbon isotopes (δ13C values)
• “You are what you
eat”
• Calcifying gland is a C
fixing organ
Briones et al. (2008)
Earthworm secreted calcite granules as a palaeoenvironmental proxy 11

12. Experiment 1
• 3 soils (C3 and C4
vegetation)
• 3 types of water (England,
Fiji, Norway)
• Constant temperature
(17 °C)
• 4 months
• 4 replicates
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13. Isotope analyses
Delta V advantage IRMS
• Flash EA 1112 HT
– δ2H and δ18O in water, soils,
manure, earthworms
• GasBench II
– δ13C and δ18O in granules,
water, DIC, CO2
SerCon
– δ13C and δ15N in soils, manure,
DOC, DON
Earthworm secreted calcite granules as a palaeoenvironmental proxy 13

14. Granule δ18O vs. δ13C
evaporation
adaptation to food
~3 ‰
Earthworm secreted calcite granules as a palaeoenvironmental proxy 14

15. δ13C in soils
adaptation to food
~3 ‰
Earthworm secreted calcite granules as a palaeoenvironmental proxy 15

16. δ13C in soils and granules
Earthworm secreted calcite granules as a palaeoenvironmental proxy 16

17. Reconstructed δ18Owater
Earthworm secreted calcite granules as a palaeoenvironmental proxy 17

18. Earthworm secreted calcite granules as a palaeoenvironmental proxy 18

19. Conclusions
• δ18O values of granules appear to
reflect ambient water
• δ13C values of granules adapt to
δ13C values of food (manure)
over < 1 month
• So far no evident link between
soil and granule δ13C values
→ more data needed
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20. Experiment 2
• 2 soils
• 3 types of water (England,
Fiji, Norway)
• 3 temperatures (10, 16,
21 °C)
• 3 weeks acclimatisation
• 1 month
• 6 replicates
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21. Future work
More analyses:
• Water δ13C, δ18O
• δ2H, δ15N
• More granules
Application on archaeological and geological samples
• Reconstruction of past temperatures
• Dating of samples by U/Th
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22. Thank you!
Questions?
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