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

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. Protistan Microfossils
Foraminifera - sarcodina (amoeba)
Protistan Microfossils

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

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

8. Protistan Microfossils
Foraminifera
Planktic forams
Calcite
Protistan Microfossils

9. Protistan Microfossils
Radiolarians - Spumellarians
Protistan Microfossils
Silica

10. Protistan Microfossils
Radiolarians - Nacellarians
Protistan Microfossils
Silica

11. 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.

12. Ostracods - Arthropoda
Animal Microfossils
calcite

13. Conodonts - Vertebrata
Animal Microfossils

14. Conodonts - Vertebrata
conodont apparatus
Animal Microfossils

15. Conodonts - Vertebrata
Animal Microfossils

16. Animal Microfossils Conodonts - Vertebrata microwear facets
calcium phosphate

17. 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).

18. Coccolithophorids - Haptophyta
calcite
Algal Microfossils

19. Chalk Cliffs, England

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

21. Diatoms - Chrysophyta
silica
frustules
Algal Microfossils

22. Diatoms - Chrysophyta
silica
Algal Microfossils

23. Algal Microfossils Dinoflagellates - Pyrrhophyta Sporopollenin living

25. Dinoflagellates - Pyrrhophyta
Living cell
Cyst

28. 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.

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

30. Coccoliths
From Sugarman, et. al, 1995

31. Foraminifera
From Sugarman, et. al, 1995

32. Deep Sea Drilling Project ship - Glomar Challenger

33. Recovering sediment cores from the deep ocean.

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

37. Stable Isotopes Oxygen O16 O18 CO2 + H2O = HCO3-1 + H+
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.

38. Mass Spectrometer

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

40. Modern sea-surface temperature

41. d18O due to ice buildup less ice negative excursion more ice
Glaciations cause more d18O to accumulate in seawater.
This happens because 16O evaporates preferentially and becomes trapped on land as glacial ice.
less ice
negative excursion
H216O
more ice
positive excursion

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

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

45. Navesink Formation, central New Jersey

46. 70X
Benthic foraminifera

47. 70X
Benthic foraminifera

48. 70X
Planktic foraminifera

49. 70X
Ostracod

50. 70X
Ostracod valve

51. 70X
Burrowing echinoid spine

52. 70X
Fish denticle