Quaternary Environments Marine Sediments and Corals

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Quaternary EnvironmentsMarine Sediments and
Corals
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Marine Environments

• Cover more than 70 of the Earths surface
• Between 6-11 billion metric tons of sediment
  accumulate in the ocean basins annually

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Definitions

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

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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

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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.

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Sedimentation in the Ocean
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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

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Regions Usable for Foram Studies
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Important Organisms

• Foraminifera - Zooplankton
• Coccolithophores (coccoliths) Unicellular algae
• Dinoflagellate Organic walled
• Radiolarians Siliceous zooplankton
• Silicoflagallates Siliceous
• Diatoms Siliceous algae

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Foraminifera Globigerina bulloides from the
Labrador Sea
Foraminifera Neogloboquadrina pachyderma from
the North Atlantic
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Coccolith
Dinoflagellate
Centric Diatom
Pennate Diatom
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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

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Benthic 18O record for equatorial Atlantic for
the past 3.2 Mya
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SST Reconstructions for 18,000 yrs BP
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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

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Drilling corals for paleoclimatic reconstruction.
http//www.noaanews.noaa.gov/magazine/stories/mag9
5.htm
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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
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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

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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

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Long Coral Based Records of Past Climate
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