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Quaternary Environments Marine Sediments and Corals

Quaternary Environments Marine Sediments and Corals. Marine Environments. Cover more than 70% of the Earth’s surface Between 6-11 billion metric tons of sediment accumulate in the ocean basins annually. Definitions.

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Quaternary Environments Marine Sediments and Corals

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  1. Quaternary EnvironmentsMarine Sediments and Corals

  2. Marine Environments • Cover more than 70% of the Earth’s surface • Between 6-11 billion metric tons of sediment accumulate in the ocean basins annually

  3. Definitions • Planktic – Passively floating organisms living near the surface (0-200m depth) • Benthic – Bottom-dwelling organisms • Test – Protective covering

  4. CLIMAP • The CLIMAP Research Group • Climate: Long-range Investigation, Mapping, and prediction (CLIMAP) • SST and Ocean Surface Conditions • From 635 ocean sediment cores • Data from faunal counts of diatoms, planktonic foraminifera, coccoliths, and radiolaria • Stratigraphy - percent fine, coarse, total carbonate, 18O and 13C • Geochemistry - percent opal, quartz, and organic carbon

  5. SPECMAP • Spectral Mapping Project • Determining the spectral characteristics of ocean sediment-based paleoclimatic records • Establishing a basic timeframe for past climatic events • Climate times series of the past 400,000 years • Based on 17 sediment cores from the Atlantic Ocean. • Quantitative data on planktonic species and assemblages which reflect conditions in the surface waters of the Atlantic Ocean • 18O, 13C difference (planktic and benthic), and Cd/Ca.

  6. Sedimentation in the Ocean

  7. Problems With Marine Sediments • Selective dissolution of thin-walled specimens • Transportation by ocean currents • Removal of easily transported species • Introduction of exotics • These problems may make some ocean floor sediments unsuitable for paleoclimatic reconstructions

  8. Regions Usable for Foram Studies

  9. Important Organisms • Foraminifera - Zooplankton • Coccolithophores (coccoliths) – Unicellular algae • Dinoflagellate – Organic walled • Radiolarians – Siliceous zooplankton • Silicoflagallates – Siliceous • Diatoms – Siliceous algae

  10. Foraminifera – Globigerina bulloides from the Labrador Sea Foraminifera – Neogloboquadrina pachyderma from the North Atlantic

  11. Coccolith Dinoflagellate Centric Diatom Pennate Diatom

  12. Paleoclimatic Inferences • Oxygen isotopic composition of CaCO3 in foram tests • Quantitative interpretations of species assemblages and their spatial variations through time • Morphological variations in particular species resulting from environmental factors

  13. Benthic 18O record for equatorial Atlantic for the past 3.2 Mya

  14. SST Reconstructions for 18,000 yrs BP

  15. Coral Records of Past Climate • Reef-Building Massive Corals that have a symbiotic relationship with algae • The algae produce carbohydrates through photosynthesis and are therefore dependent upon water depth, turbidity, and cloudiness • Sectioned and x-rayed • High and low density bands can be distinguished with high-density bands relating to high SST

  16. Drilling corals for paleoclimatic reconstruction. http://www.noaanews.noaa.gov/magazine/stories/mag95.htm

  17. Growth bands in Coral. Arrows indicate "stress bands" revealed in an x-ray of coral skeletal material caused by cold, unfavorable temperatures. http://www-ocean.tamu.edu/Quarterdeck/QD6.2/giese.html

  18. Benefits of Coral Analysis • Tropical records that fill gaps left by other marine paleorecords • Annual resolution • Dating is checked with 230Th • Possible extent back to 130,000 years BP

  19. Problems with Coral Analysis • Few records that extend past one century • Real extreme events may go unrecorded do to death of the coral colony for some period of time

  20. Long Coral Based Records of Past Climate

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