Unit5 Microfossils

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Spores & Pollen

  • Composed of sporopollenin
  • Size ranges between 10 - 200 microns in diameter
  • Produced in plants that either lived on land or in a marginal shallow water environment
  • Spores
    • Produced by plants (such as mosses and ferns)
    • Earliest preserved terrestrial plants are from the late silurian
      • Though spores were found earlier in the ordovician
  • Pollen
    • Product of seed bearing plants
    • Earliest pollen producing plants were from the late devonian
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Radiolaria

  • Planktonic mode of life
  • Size ranges from 30µm to 2mm
  • Occupied niches near the surface to hundreds of metres deep
  • Have a rich diversity of delicate silica skeletons
    • Therefore preserved at depths below the carbon compensation depth (ccd) and are easy to recover
  • Have been around since the late precambrian
    • Great stratigraphic tool
    • Great palaeo-envirionmental tool
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Conodonts - Extinct

  • The teeth of a soft-bodied creature
    • thought to be similar to a hagfish
  • Composed of calcium phosphate
  • Size ranges from 200µm to 5mm
  • Earliest are found in precambrian rocks
  • Died out in the permo-triassic extinction event
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Ostracods

  • Complex crustaceans, related to trilobites and crabs
  • They have similar morphological features to bivalves:
    • Two valves
    • A hinge with teeth and sockets
    • aductor muscles to close the valves
  • Usually less than 2mm in length
  • Shell (carapace) made of chitin or calcium carbonate
  • Range from cambrian to the present day
  • Mainly a benthonic mode of life
  • Good palaeo-environmental indicators
    • As they have different forms in waters of the entire range of salinity
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Foraminifera

  • Mostly simple single-celled creatures with a protective shell (test)
  • Composed of calcium carbonate
  • They range in size from 1µm to around 110mm
  • Modern foraminifera capture their food using thread-like structures
    • Which extend through holes in the test
  • Most forms are benthonic (sessile or vagrant)
    • But a few are planktonic (such as globigerina)
  • They range from early cambrian to the present day
    • Although planktonic forms were not common untill the mesozoic
  • Excellent stratigraphic tool (used extensively in the oil industry)
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