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Micropalaeontology Intro (Foraminifera (Protists (single-celled organisms,…
Micropalaeontology Intro
Foraminifera
Crucial microfossil group for understanding K/T boundary
Protists
single-celled organisms
1 mm or so
Still thrive in modern oceans
Herbivores / Omnivores
Lifespan ~ 1 month
Zooplankton which feeds on phytoplankton
Rhizopodea group
Foram Morphology
Calcite shell
Protoplasm inside
Protoplasm expelled along spines & holds other organisms i.e. diatoms
Spines radiate from shell
Death - only main shell preserved
Foram Ooze
sediment composed solely of foram shells
over Myr builds up sequence like White Cliffs of Dover
sedimentary sequences used for dating
Why microfossils so interesting ?
Biodiversity / Earth system indicators
shaped by interaction btwn
geological,
biological,
climate
external events
biodiversity = number of species / species diversity
Cretaceous-Paleogene Boundary
Discovered by analysis of microfossils & sediment particles
Cause = huge meteor impact on Earth
bolide = large meteor
caused mass extinction
Causes of Mass Extinctions
Meteorite Impacts
K/T Boundary
Outgassing of LIPs
Permo-Triassic Boundary
Climate
End-Ordivician - glaciation?
Other
Biological factors?
Viruses?
Hard to study - little evidence
Mass Extinctions vary greatly in
size
impact
cause
Name
Cretaceous-Tertiary = K/T
Cretaceous-Paleogene = K/Pg
Tertiary = Cenozoic
Units Around K/T boundary
Ejectite
(bottom)
material blown into atmos in molten state by impact
cooled and recrystallised on returning
tectites
- tear-shaped
Tsunamite
(mid)
sandstone with huge wave ripples
records super tsunami generated by impact
Iridium layer
finer material (dust/ash) fell later through water column
dust rich in extraterrestrial iridium
accumulated gradually on seafloor
K/T Boundary
New Gulf of Mexico Core
Green glassy tectite layer
Paleogene overlies tectite layer
K/T Debate
Keller Claims 2 Impacts
claimed unconformity below the tectite layer
hence evidence of one impact = lost
quotes biostratigraphy from Atlantic
big hiatus of 400 ka below tectite?
Kroon Persists Only 1 Impact
Bio event is localised (only seen in Tropics)
Would not expect to see signal in the Atlantic