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Marine Microfossils

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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Marine Microfossils

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  1. Dr. J Bret Bennington Department of Geology Marine Microfossils

  2. 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.

  3. 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.

  4. Foraminifera - sarcodina (amoeba) Protistan Microfossils

  5. Foraminifera - sarcodina (amoeba) • Benthic forams • live in sediments • relatively large • Planktic forams • live floating in the water column • relatively small Protistan Microfossils

  6. Foraminifera - sarcodina (amoeba) Benthic forams Protistan Microfossils Calcite

  7. Foraminifera Planktic forams Calcite Protistan Microfossils

  8. Radiolarians - Spumellarians Protistan Microfossils Silica

  9. Radiolarians - Nacellarians Protistan Microfossils Silica

  10. 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.

  11. Ostracods - Arthropoda Animal Microfossils calcite

  12. Conodonts - Vertebrata Animal Microfossils

  13. Conodonts - Vertebrata conodont apparatus Animal Microfossils

  14. Conodonts - Vertebrata Animal Microfossils

  15. microwear facets Conodonts - Vertebrata Animal Microfossils calcium phosphate

  16. 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).

  17. Coccolithophorids - Haptophyta calcite Algal Microfossils

  18. Chalk Cliffs, England

  19. Diatoms - Chrysophyta silica Pennate - benthic, parasitic Centric - planktic Algal Microfossils

  20. frustules Diatoms - Chrysophyta silica Algal Microfossils

  21. Diatoms - Chrysophyta silica Algal Microfossils

  22. Dinoflagellates - Pyrrhophyta Sporopollenin living fossil Algal Microfossils

  23. Dinoflagellates - Pyrrhophyta Living cell Cyst

  24. 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.

  25. From Sugarman, et. al, 1995 Biostratigraphic zones - intervals of time defined by the presence of particular fossil species.

  26. Coccoliths From Sugarman, et. al, 1995

  27. Foraminifera From Sugarman, et. al, 1995

  28. Deep Sea Drilling Project ship - Glomar Challenger

  29. Recovering sediment cores from the deep ocean.

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

  31. 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.

  32. Mass Spectrometer

  33. Increasing 18O in calcite relative to water Change in isotopic ratio in carbonate shell with change in water temperature.

  34. Modern sea-surface temperature

  35. 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

  36. warming cooling Average d18O curve from 5 deep sea cores (foram calcite). After Imbrie et al. (1984)

  37. Onset of Cenozoic cooling trend - development of cold deep ocean circulation.

  38. Navesink Formation, central New Jersey

  39. 70X Benthic foraminifera

  40. 70X Benthic foraminifera

  41. 70X Planktic foraminifera

  42. 70X Ostracod

  43. 70X Ostracod valve

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