Week 6 - Microfossils Flashcards
What are the main learning outcomes of microfossil studies?
Constructing age-depth models, calculating sedimentation rates, identifying breaks in sedimentation, and understanding biostratigraphy.
What defines a microfossil?
Any fossilized part of an organism (usually skeletal) ranging from <1 μm to >1 mm in size.
What are the two main types of microfossils based on cellular structure?
Single-celled (e.g., radiolarians, foraminifera) and multicellular (e.g., ostracods).
How do microfossils obtain energy?
They can be photosynthetic (e.g., diatoms, coccolithophores)
heterotrophic (e.g., foraminifera, radiolarians),
or a combination of both.
What are the different scales used to measure microfossils?
1000 μm (1 mm): Visible to the eye, microscope needed for details.
100 μm (0.1 mm): Invisible to the eye, requires a light microscope.
1 μm (1000 nm): Requires high magnification (light or electron microscopes).
What are the three main uses of microfossils in geology?
Biostratigraphy – Dating rocks by identifying fossil species.
Palaeoclimate/Palaeoenvironment – Reconstructing past climate and ocean conditions.
Evolutionary Studies – Understanding evolutionary history through fossil records.
What are the three main types of microfossils based on composition?
Calcareous (CaCO₃) – Foraminifera, calcareous nannofossils, ostracods, pteropods.
Siliceous (SiO₂) – Diatoms, radiolarians.
Organic-walled – Dinoflagellates, acritarchs, chitinozoa, pollen.
What are calcareous nannofossils primarily composed of?
Calcium carbonate (CaCO₃), usually in the form of calcite.
What is the main group of calcareous nannofossils?
Coccolithophores.
What is the size range of calcareous nannofossils?
~5 – 10 μm.
Where are calcareous nannofossils commonly found?
Marine environments; they make up chalk deposits like the White Cliffs of Dover.
What are foraminifera?
Single-celled protists with CaCO₃ shells, found in both planktonic and benthic environments.
What is the size range of foraminifera?
50 μm – 2 mm (usually).
What are the two main types of foraminifera?
Planktic foraminifera – Float in the ocean; delicate, thin shells.
Benthic foraminifera – Live on the sea floor; thicker shells.
How are foraminifera used in geology?
For biostratigraphy, ocean temperature reconstructions, and geochemical analysis.
What are ostracods?
Microscopic crustaceans with bivalved calcite carapaces.
What is the size range of ostracods?
0.2 mm – 2 mm (up to 30 mm in rare cases).
What are pteropods?
Planktonic molluscs with aragonite shells.
What is the size ranges of pteropods?
0.2 mm – 5 mm (up to ~30 mm).
What are diatoms?
Photosynthetic algae with opaline silica (SiO₂) skeletons.
What is the size range of diatoms?
20 – 200 μm (up to 2 mm).
What is the economic importance of diatoms?
They form diatomaceous earth, used in filters, toothpaste, paints, and insecticides.
What are radiolarians?
Zooplankton with silica skeletons, floating at all ocean depths.
What are the size ranges of Radiolarians?
100 – 300 μm.
