Week 7 - K-Pg Boundary Flashcards
What were the climate trends during the Late Cretaceous (~100-66 Ma)?
Warm and wet, but slightly cooler than the mid-Cretaceous thermal maximum.
What major oceanic changes occurred during the Late Cretaceous?
The North and South Atlantic Oceans were opening, and the Tethys Ocean was slowly closing.
What continents were moving northward in the Late Cretaceous?
India and Australia.
How do we know global temperatures were higher in the Late Cretaceous?
Coniferous forests extended into polar regions.
What were the climate trends in the Early Paleogene (~66-56 Ma)?
Climate remained warm but showed cooling trends.
What was the Early Eocene Climatic Optimum (EECO)?
A warm period occurring around 53-50 Ma.
What percentage of species and genera went extinct during the K-Pg mass extinction?
~75% of species, ~30% of genera.
What ecosystems were affected by the K-Pg mass extinction?
Both marine and terrestrial ecosystems.
Name some major victims of the K-Pg mass extinction.
Non-avian dinosaurs, pterosaurs, mosasaurs, ammonites, belemnites, rudist bivalves.
What primary producers were heavily affected during the K-Pg mass extinction?
Planktonic foraminifera, coccolithophores, some land plants.
How did the K-Pg extinction affect the carbon cycle?
It caused major disruptions, affecting ocean chemistry and food chains.
Name some survivors of the K-Pg extinction.
Birds, small mammals, crocodiles, sea turtles, insects, worms, snails, amphibians.
What traits likely helped species survive the K-Pg extinction?
Adaptability, burrowing behavior, and detritus-based food chains.
How many global boundary sections exist for the K-Pg extinction?
About 350 sites worldwide.
Name three key lithological markers of the K-Pg boundary.
Iridium layer, shocked quartz & microtektites, boundary clay layer.
What does a high concentration of iridium at the K-Pg boundary suggest?
An asteroid impact, as iridium is rare on Earth but abundant in asteroids.
What do shocked quartz and microtektites indicate?
High-energy impact events.
What does the boundary clay layer indicate?
Sudden sedimentary change due to environmental upheaval.
Where is the Chicxulub crater located?
Yucatán Peninsula, Mexico.
How large is the Chicxulub crater?
150 km in diameter, formed by a 10 km-wide asteroid.
What key evidence supports the Chicxulub impact hypothesis?
Iridium anomaly, shocked quartz, microtektites, and ejecta layer (glass spherules).
What short-term environmental consequence followed the impact?
“Impact winter” caused by dust blocking sunlight.
What long-term effects did the Chicxulub impact have on the climate?
Increased CO₂ and sulfur emissions led to acid rain and ocean acidification.
How did global wildfires contribute to climate change after the impact?
They released massive amounts of CO₂, worsening climate effects.
Where are the Deccan Traps located?
India.
What gases did the Deccan Traps volcanism release?
CO₂, SO₂, and aerosols.
How did Deccan Traps volcanism affect climate before and after the impact?
Gradual warming before, but cooling afterward due to sulfate aerosols.
What is the key question regarding Deccan Traps volcanism?
Was volcanism a primary cause of extinction or did it only worsen conditions?
Which hypothesis is considered stronger for explaining the K-Pg extinction?
Chicxulub impact is the primary extinction driver, with Deccan Traps playing a secondary role.
How much did global temperatures rise during the PETM?
~5-8°C over <10,000 years.
What was the main cause of PETM climate change?
Massive carbon release into the oceans and atmosphere.
What happened to ocean acidity during the PETM?
Ocean acidification caused shoaling of the Carbonate Compensation Depth (CCD).
What happened to calcium carbonate (CaCO₃) in deep-sea sediments during the PETM?
It decreased due to acidification.
Which marine organisms suffered mass extinction during the PETM?
Benthic foraminifera.
How did planktonic foraminifera and calcareous nannoplankton respond to PETM?
They shifted their distribution patterns.
How did terrestrial plant life respond to PETM?
Warmer-adapted plants expanded poleward.
What effect did PETM have on early mammals?
Caused mammalian dwarfism and accelerated diversification.
What were three potential carbon sources for the PETM?
1) NAIP volcanism,
2) Methane hydrate dissociation, 3) Permafrost & peat oxidation.
