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Dr. J Bret Bennington Department of Geology. Marine Microfossils. 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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what are marine microfossils
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.
protistan microfossils
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.
slide4

Foraminifera - sarcodina (amoeba)

Protistan Microfossils

slide5

Foraminifera - sarcodina (amoeba)

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

Protistan Microfossils

slide7

Foraminifera - sarcodina (amoeba)

Benthic forams

Protistan Microfossils

Calcite

slide8

Foraminifera

Planktic forams

Calcite

Protistan Microfossils

slide9

Radiolarians - Spumellarians

Protistan Microfossils

Silica

slide10

Radiolarians - Nacellarians

Protistan Microfossils

Silica

animal microfossils
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.
slide12

Ostracods - Arthropoda

Animal Microfossils

calcite

slide13

Conodonts - Vertebrata

Animal Microfossils

slide14

Conodonts - Vertebrata

conodont apparatus

Animal Microfossils

slide15

Conodonts - Vertebrata

Animal Microfossils

slide16

microwear facets

Conodonts - Vertebrata

Animal Microfossils

calcium phosphate

algal microfossils
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).
slide18

Coccolithophorids - Haptophyta

calcite

Algal Microfossils

slide20

Diatoms - Chrysophyta

silica

Pennate - benthic, parasitic

Centric - planktic

Algal Microfossils

slide21

frustules

Diatoms - Chrysophyta

silica

Algal Microfossils

slide22

Diatoms - Chrysophyta

silica

Algal Microfossils

slide23

Dinoflagellates - Pyrrhophyta

Sporopollenin

living

fossil

Algal Microfossils

why are marine microfossils useful
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 Earth’s history.
slide29

From Sugarman, et. al, 1995

Biostratigraphic zones - intervals of time defined by the presence of particular fossil species.

slide30

Coccoliths

From Sugarman, et. al, 1995

slide31

Foraminifera

From Sugarman, et. al, 1995

slide34

Foraminifera

  • Fossil foram species can be used to date age of seafloor and sediment layers.
slide37

O16

O18

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.
slide39

Increasing 18O in calcite relative to water

Change in isotopic ratio in carbonate shell with change in water temperature.

slide41

less ice

negative excursion

more ice

positive excursion

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

slide42

warming

cooling

Average d18O curve

from 5 deep sea cores

(foram calcite).

After Imbrie et al. (1984)

slide46

70X

Benthic foraminifera

slide47

70X

Benthic foraminifera

slide48

70X

Planktic foraminifera

slide49

70X

Ostracod

slide50

70X

Ostracod valve

slide51

70X

Burrowing echinoid spine

slide52

70X

Fish denticle

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