Cretaceous-Tertiary (K-T) mass extinction
- Created by: Brad_ers_B
- Created on: 19-04-15 17:08
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- Cretaceous-Tertiary (K-T) mass extinction
- What do we know?
- Around 65 million years ago
- 75% of species became extinct
- Marine = large reptiles, brachiopods, ammonites, coccoliths, foraminfera, belemnites, fish and some bivalves
- Land = Dinosaurs, pterosaurs and plants
- Animals like crocodiles, turtles, lizards, mammals and birds survived without many casualties
- It was gradual showing decline in species over several million years before
- Similar to Permo-Triassic
- Impact of an asteroid or meteorite
- Layer of iridium (transition element rare on Earth)
- Found concentrated in clays at boundary
- Shocked grains of quartz
- Usually found around impact craters
- Tektites have a very low water content suggesting not Earth formed or formed as the rock melted quick on impact
- Large-scale sedimentary evidence in Texas of a large tsunami
- Large meteorite crater found on the Yucatan Peninsula in Mexico at Chicxulub
- Shown by gravity variations in the region
- Circular depression around 180km in diameter
- Layer of iridium (transition element rare on Earth)
- Major volcanic activity (Deccan Traps)
- Enormous series of eruptions in India
- Covered area of roughly 500,000km2
- The volcanism was probably the same as with Siberian Traps
- Enormous series of eruptions in India
- What do we know?
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