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Comparing rock and fossil records in the deep sea


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Comparing rock and fossil records in the deep sea

  1. 1. Comparing rock and fossil records in the deep seaGraeme T. Lloyd, Andrew B. Smith and Jeremy R. Young
  2. 2. Fossil record is our only record of the diversification of life
  3. 3. Diversity correlates with rock record on landPeters and Foote 2001 Smith and McGowan 2007
  4. 4. An alternative record• Calcareous microfossils such as coccolithophores have land-based and deep sea records• i.e., two diversity records and two rock records• What is the relationship between these records?• How much does the rock record influence diversity patterns?
  5. 5. The database• Study groups are Coccolithophores and planktic Foraminifera• Novel compilation from North Atlantic• Compiled from 40 years ODP/DSDP data• 64,077+ occs from 20,723+ samples• High temporal resolution (biozones)
  6. 6. Deep sea species richness
  7. 7. Deep sea genus richness
  8. 8. Deep sea rock record
  9. 9. Correlation tests• First both time series were log-transformed• Long term test: – Simple correlation• Short term tests: – First differences (absolute) – Moving average differences (relative to long term trend)• Degree (rho) and significance (p) of correlations determined using Spearman rank
  10. 10. Deep sea long-term correlation
  11. 11. Deep sea short-term correlation I
  12. 12. Deep sea short-term correlation I
  13. 13. Deep sea short-term correlation II
  14. 14. Deep sea short-term correlation II
  15. 15. Modeling
  16. 16. Modeling results
  17. 17. Modeling results
  18. 18. Subsampling
  19. 19. Subsampling results
  20. 20. Conclusions• Deep sea diversity curve largely explicable by sampling• Apparent rise in nannofossil diversity to present strongly associated with rise in sampling
  21. 21. The other side of the story• What about the land-based record for the same groups?• Sampling strategy based on distribution charts from primary literature• Rock record measure is number of localities
  22. 22. Two rock records
  23. 23. Two fossil records
  24. 24. Summary• Both land and sea have measurable rock biases that follow different trajectories over geological time• Will allow a clear and explicit test of how important a role these play in shaping our fossil record