Egu2008

380 views

Published on

Presentation given at the EGU conference in Vienna April 13-18 2008

Published in: Education
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
380
On SlideShare
0
From Embeds
0
Number of Embeds
5
Actions
Shares
0
Downloads
0
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Egu2008

  1. 1. Stable oxygen isotopes in freshwater mussels (Unionidae) as a proxy for late Holocene floods and droughts of Rhine and Meuse Emma Versteegh Hubert Vonhof Simon Troelstra Dick Kroon
  2. 2. Freshwater mussels <ul><li>Common </li></ul><ul><li>Archaeological finds </li></ul><ul><li>Museum collections </li></ul><ul><li>Seasonal growth increments </li></ul><ul><li>Precipitate  18 O in shell carbonate; shell  18 O depends on: </li></ul><ul><ul><li>T </li></ul></ul><ul><ul><li>Water  18 O </li></ul></ul><ul><li>Species: Unio crassus , U. pictorum , U. tumidus </li></ul>
  3. 3. Stable oxygen isotopes
  4. 4. Rivers Rhine and Meuse
  5. 5. δ 18 O rivers Glacier melting High discharge Flood Dry summer
  6. 6. Aim <ul><li>Address the possibilities for shell δ 18 O as a proxy for river discharge and flood and drought frequencies in Meuse and Rhine: </li></ul><ul><li>Do growth lines in the shells correspond to yearly winter growth cessations? </li></ul><ul><li>The temperature lower limits below which growth cessation occurs. </li></ul><ul><li>Do the shells of two species precipitate aragonite in isotopic equilibrium with the ambient water, i. e. predicted values correspond to measured values? </li></ul><ul><li>Can past river floods and droughts be reconstructed from shell δ 18 O? </li></ul>
  7. 7. Methods <ul><li>Microsampling </li></ul><ul><ul><li>Merchantek Micromill </li></ul></ul><ul><li>Stable isotopes </li></ul><ul><ul><li>Finnigan MAT 252 </li></ul></ul><ul><ul><li>Finnigan Delta </li></ul></ul><ul><li>Water sampling </li></ul>
  8. 8. Setup of the project <ul><li>Monitoring experiment </li></ul><ul><li>20 th century shells </li></ul><ul><li>Late Holocene shells </li></ul>
  9. 9. Monitoring experiment <ul><li>Cages with living mussels in fish ladders </li></ul><ul><li>- Hagestein (Lek) </li></ul><ul><li>- Lith (Meuse) </li></ul>
  10. 10. 20 th century shells <ul><li>Meuse: </li></ul><ul><li>Grevenbicht 1998 </li></ul><ul><li>Lith 2005 </li></ul><ul><li>Kerkdriel 2005 </li></ul><ul><li>Rhine distributaries </li></ul><ul><li>Tuil 1998 (Waal) </li></ul><ul><li>Herwijnen 2003 (Waal) </li></ul><ul><li>Hurwenen 2003 (Waal) </li></ul><ul><li>Hagestein 2005 (Lek) </li></ul>
  11. 11. Late Holocene shells
  12. 12. Palaeogeography
  13. 13. Results Average δ 18 O per shell
  14. 14. Seasonal patterns Slowing down of growth
  15. 15. 20 th century shells
  16. 16. Predicted shell δ 18 O <ul><li>Water δ 18 O & T  shell δ 18 O </li></ul>Grossman & Ku (1986); Dettman et al. (1999)
  17. 17. Measured δ 18 O vs. Predicted δ 18 O
  18. 18. Measured δ 18 O vs. Predicted δ 18 O: 20 th century shells Juvenile stage
  19. 19. Measured δ 18 O vs. Predicted δ 18 O: 20 th century shells Glacier melting Dry summer ???
  20. 20. Measured δ 18 O vs. Predicted δ 18 O: monitoring
  21. 21. Late Holocene shells
  22. 22. Conclusions <ul><li>The shells do not grow in winter </li></ul><ul><ul><li>Winter floods are not recorded </li></ul></ul><ul><li>Growth lines usually correspond to winter growth stops, but not always! </li></ul><ul><li> 18 O shell corresponds well with predicted values </li></ul><ul><li>  18 O shell is useful proxy </li></ul><ul><li>300 - 4500 year old shells show seasonal stable isotope patterns similar to modern shells </li></ul><ul><ul><li> no diagenesis </li></ul></ul>
  23. 23. <ul><li>Thank you! </li></ul>

×