Marine Microfossils

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Marine Microfossils
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What are marine microfossils?

• Fossilized remains of small organisms or tiny
  hardparts of larger organisms.
• Plankton
• Benthic fauna
• Many different groups representing animals,
  protists, and a variety of algae.

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Protistan Microfossils

• Mineralized test (shell) formed by amoeba-like
  protozoans.
• Foraminifera - calcareous (calcium carbonate) or
  agglutinated (test composed of cemented grains of
  sand or other sediment).
• Radiolaria - test composed of silica.

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Foraminifera - sarcodina (amoeba)
Protistan Microfossils
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Foraminifera - sarcodina (amoeba)

• Benthic forams
• live in sediments
• relatively large
• Planktic forams
• live floating in the water column
• relatively small

Protistan Microfossils
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Foraminifera - sarcodina (amoeba)
Benthic forams
Protistan Microfossils
Calcite
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Foraminifera
Planktic forams
Calcite
Protistan Microfossils
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Radiolarians - Spumellarians
Protistan Microfossils
Silica
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Radiolarians - Nacellarians
Protistan Microfossils
Silica
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Animal Microfossils

• Mineralized shells and teeth produced by
  metazoans (multicellular animals).
• Ostracods - calcareous (calcium carbonate) shell
  produced by tiny crustaceans.
• Conodonts - calcium phosphate teeth produced by
  an extinct group of vermiform (worm-like)
  vertebrates.

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Ostracods - Arthropoda
Animal Microfossils
calcite
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Conodonts - Vertebrata
Animal Microfossils
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Conodonts - Vertebrata
conodont apparatus
Animal Microfossils
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Conodonts - Vertebrata
Animal Microfossils
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Conodonts - Vertebrata
Animal Microfossils
calcium phosphate
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Algal Microfossils

• Mineralized tests and plates produced by a
  variety of unicellular algae.
• Coccolithophorids - tiny algae that produce
  calcareous plates - main component of chalk.
• Diatoms - algal cells that produce paired tests
  (called frustules) composed of silica.
• Dinoflagellates - marine algae that produce
  organic cysts preserved in sedimentary rock.
  Also the cause of most harmful algal blooms
  (HABs).

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Coccolithophorids - Haptophyta
calcite
Algal Microfossils
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Chalk Cliffs, England
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Diatoms - Chrysophyta
silica
Pennate - benthic, parasitic
Centric - planktic
Algal Microfossils
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Diatoms - Chrysophyta
silica
Algal Microfossils
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Diatoms - Chrysophyta
silica
Algal Microfossils
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Dinoflagellates - Pyrrhophyta
Sporopollenin
living
fossil
Algal Microfossils
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Dinoflagellates - Pyrrhophyta
Living cell
Cyst
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Why are marine microfossils useful?

• Biostratigraphy - dating rock layers using
  fossils.
• Environmental reconstruction - identifying
  different marine environments in the past.
• Paleothermometry - determining ocean water
  temperature in the past.
• Paleoclimatology - reconstructing climate change
  through Earths history.

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From Sugarman, et. al, 1995
Biostratigraphic zones - intervals of time
defined by the presence of particular fossil
species.
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From Sugarman, et. al, 1995
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From Sugarman, et. al, 1995
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Deep Sea Drilling Project ship - Glomar Challenger
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Recovering sediment cores from the deep ocean.
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Foraminifera

• Fossil foram species can be used to date age of
  seafloor and sediment layers.

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Stable Isotopes Oxygen
99.76
.2
CO2 H2O HCO3-1 H
2 HCO3-1 Ca CaCO3 H2CO3

• O18 is preferentially removed from seawater
  during calcite formation.
• This effect is sensitive to temperature.
• Ratio of O18 / O16 in shell is temperature
  dependent.
• Can be measured using a mass spectrometer.

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Mass Spectrometer
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Increasing 18O in calcite relative to water
Change in isotopic ratio in carbonate shell with
change in water temperature.
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Modern sea-surface temperature
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d18O due to ice buildup Glaciations cause more
d18O to accumulate in seawater. This happens
because 16O evaporates preferentially and becomes
trapped on land as glacial ice.
H216O
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Average d18O curve from 5 deep sea cores (foram
calcite). After Imbrie et al. (1984)
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Onset of Cenozoic cooling trend - development of
cold deep ocean circulation.
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Navesink Formation, central New Jersey
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70X
Benthic foraminifera
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70X
Benthic foraminifera
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70X
Planktic foraminifera
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70X
Ostracod
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70X
Ostracod valve
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70X
Burrowing echinoid spine
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70X
Fish denticle