Approaches to Paleoceanography

1. Approaches to Paleoceanography

2. Approaches to Paleoceanography • Selecting Areas for Study • Coring Methods • Sampling • Proxies • Stratigraphy • Paleogeography

3. Selecting Study Sites • Regional Studies • Critical climate or circulation regimes • Sea Level • Depth Transects • Oceanic Front Migration

4. Regional Studies • These type of studies are strategies designed to look at changes in end-members or in critical/sensitive regions

5. Regional Studies • For example, the North Atlantic and Southern Oceans get a lot of attention for two reasons: • Both are sensitive surface water changes • Both are locations for deep water masses

6. CLIMAP • Climate: Long Range Investigation, Mapping, and Prediction • CLIMAP, was a major research project of the 1970s and 80s to produce a map of climate conditions during the last glacial maximum • CLIMAP has been a cornerstone of paleo-climate research and remains the most used sea surface temperature reconstruction of the global ocean during the last glacial maximum

7. CLIMAP

8. CLIMAPBased on the SST’s and vegetation reconstructions, GCM’s were run to analyze various aspects of the Earth’s climate system

9. Deep-Water Circulation • North Atlantic • Southern Ocean • Pacific • The North Atlantic and Pacific Oceans represent end-members in the Conveyor Circulation model. The Southern Ocean chemistry is a product of these end-members. Monitoring both end-members and the SO allows one to asses the relative inputs of each

11. Sea Level Studies • Ken will lecture on this in two weeks but choosing key locations to monitor the rise and fall of Sea level is important

12. Barbados, New Guinea, Tahiti

13. Polar Front • The Antarctic Convergence, also known as the Antarctic Polar Frontal Zone (or "Polar Front" for short), is a line encircling Antarctica where the cold, northward-flowing Antarctic waters sink beneath the relatively warmer waters of the sub-Antarctic. The line is actually a zone approximately 30 to 40 km wide, varying somewhat in latitude in different longitudes, extending across the Atlantic, Pacific, and Indian Oceans between the 48th and 61st parallels of south latitude. The precise location at any given place and time is made evident by the sudden change in surface temperature, which averages 2.8° C to 5.5° C.

14. Polar Front

15. Polar FrontWeekly sea ice coverage and chlorophyll concentration along 170°W from 55-75°S.

16. Polar FrontWeekly sea ice coverage and chlorophyll concentration along 170°W from 55-75°S.

17. Depth Transects • Depth Transects are required because we need to know how the whole ocean changed not just the surface (planktonic taxa) or bottom sediments changed. • Shelf, Slope, Rise and Abyssal Plain • Bathymetric features like Plateaus and Ridges

18. Shelf, Slope, Rise & Abyssal Plain • This descent into the ocean depths spans the surface to deep environments • The range in depths can be sampled/cored in a relatively short distance.

19. Shelf, Slope, Rise & Abyssal Plain

20. Shelf, Slope, Rise & Abyssal Plain I like this view because it shows that there are three drawbacks to sampling the shelf to AP for reconstructions. 1) Sedimentation is not always continuous 2) The near shore environment is brackish 3) High deposition rates of terrigenous materials dilutes microfossils

21. Bathymetric Features • Remember your first homework assignment • Ontong Java Plateau, Walvis Ridge, Ceara Rise, Ninetyeast Ridge, Kerguelen Plateau • All are located in the middle of the ocean away from the heavy dilution of terrigenous sediments • All span a range of depths that help in ocean reconstructions

22. Ontong Java PlateauWestern Equatorial Pacific

23. Ceara RiseWestern Equatorial Atlantic

24. Ceara RiseWestern Equatorial Atlantic

25. Polar FrontStudies of the opening of the Drake Passage and Tasman Plateau are thought to key marine geologic events in the development of the southern Polar Front

26. Coring Methods • Piston Coring • Gravity Coring • Multi-coring • Drilling

27. Coring Location • Before launching on a cruise these days, one must have a detailed cruise plan. If planning to drill, a key ingredient is to have seismics.

28. IODP Exp 303 • Cruise to the northern North Atlantic in 2004 • Sample the Eirik Drift

32. Gardar Drift

33. Piston CoresA Core a Day keeps Doc Away

34. Piston Cores

35. Piston Cores

36. Piston Cores

37. Gravity Cores

38. Ocean Drilling Program

39. Ocean Drilling ProgramRotary coring

40. Ocean Drilling Program Cores

41. Multicorerused for multiple undisturbed coring of sediments from the ocean floor

42. Multicorer

43. Sampling • Depends on needs • Foraminifer Studies vs Calcareous Nannos • Geochemistry • Paleomagnetics

44. Proxies • Lithics • Geochemistry • Faunal and floral studies • Paleomagnetics

45. Stratigraphy • We have covered the Biostratigraphy and magnetostratigraphy. • Remember that Biostratigraphy is based on the idea that evolutionary appearances and extinctions are synchronous • Magnetostrat relies on pattern recognition since you have only positive and negative anomalies

46. Eurypterid Stratigraphy

48. Stratigraphy • Chemo-stratigraphy is based on the idea that changes in certain geochemical proxies are global. • Examples are Oxygen isotopes, Sr-isotopes

50. Sr-Isotope Record for the Phanerozoic