lab/lecture 1: microfossils Flashcards
(20 cards)
What are microfossils?
Fossilized remains of small organisms or tiny hard parts of larger organisms, including plankton, benthic fauna, and representatives from animals, protists, and algae.
What are calcareous microfossils? Give examples.
Microfossils made of calcium carbonate (CaCO₃). Examples: Coccoliths, Foraminifera, Calcareous dinoflagellate cysts, Ostracods.
What are siliceous microfossils? Give examples.
Microfossils made of opal (SiO₂). Examples: Diatoms, Radiolarians, Silicoflagellates, Sponge spicules.
Name phosphate microfossils.
Conodonts, scolecodonts (“worm jaws”), shark teeth/spines, and other fish remains (ichthyoliths).
What are organic microfossils studied under? Give examples.
Studied under palynology. Examples: Pollen, spores, chitinozoans, dinoflagellates, fungal remains.
Describe Foraminifera.
Amoeba-like protozoans with mineralized tests (shells); calcareous or agglutinated (sand-cemented).
describe benthic foraminifera
larger. Live in sediments on or within the seafloor sediments in a wide range of marine environments, from shallow coastal areas to deep ocean trenches
describe planktic foraminifera
smaller. Float in the upper water column (photic zone) of the ocean, specifically near the thermocline
What are Radiolarians?
Protozoans with silica skeletons; include Spumellarians (spherical) and Nassellarians (elongated).
describe spumellarian radiolarians
radially symmetrical, silica-based skeletons, which are often spherical or concentric and are abundant in the world’s oceans, dating back to the lower Cambrian period
describe nassellarian radiolarians
a group of radiolarians, specifically a subgroup within the Polycystina, characterized by their siliceous, cone-shaped, and elongate skeletons, often with complex, latticed structures.
What are Ostracods?
Tiny crustaceans with calcareous shells (calcite). live in a wide array of aquatic and semi-terrestrial environments, including oceans, freshwater bodies, and even moist soils.
Describe Conodonts.
Calcium phosphate “teeth” from extinct worm-like vertebrates; used in biostratigraphy. the animal lived in ancient oceans from the Cambrian to the Triassic periods
another example of conodont vertebrata
What are Coccolithophorids?
Algae producing calcareous plates (calcite); main component of chalk. found in the upper layers of the ocean, thriving in both temperate and tropical waters, particularly in areas with low nutrient concentrations and calm, surface waters
Describe Diatoms.
Algae with silica frustules (tests); benthic (pennate) or planktic (centric). found in nearly all aquatic habitats, including fresh and marine waters, soils, and moist surfaces, and are restricted to the photic zone (water depths down to about 200m) due to their need for sunlight for photosynthesis
What are Dinoflagellates?
Marine algae producing organic cysts (sporopollenin); cause harmful algal blooms (HABs). found in a wide array of aquatic environments, including oceans, freshwater ponds, rivers, streams, and even snow and ice
List 4 uses of microfossils.
Biostratigraphy (dating rock layers).
Environmental reconstruction (past marine conditions).
Paleothermometry (past ocean temperatures via δ¹⁸O ratios).
Paleoclimatology (climate change history).
How does δ¹⁸O in foraminifera shells indicate temperature?
More ¹⁸O in calcite = colder water; ¹⁶O evaporates preferentially and gets trapped in glacial ice.
What does the Cenozoic cooling trend show in microfossil records?
Development of cold deep-ocean circulation, reflected in planktic/benthic foraminifera δ¹⁸O ratios.
