Cenozoic Flashcards
What is the K-T Extinction?
The best studied mass extinction (now called K-P for Paleogene), marking the extinction of ammonites, non-bird dinosaurs, marine reptiles, and flying reptiles among other groups.
What the iridium evidence for the KT Extinction?
The main evidence for an extraterrestrial impact is the presence of an Iridium Anomaly at this age in sediments around the world. The amounts of iridium found in rocks at the KT boundary are between 20-160x higher than the amount in typical crustal rocks. Iridium is rare in the earth’s crust, but it is common in meteorites in the earth’s mantle. It is believed that the extinction is caused by a meteor or asteroid about 10-20 km in diameter (by how much iridium is found), it is believed to have landed in the Yucatan Peninsula.
What is the crater where the KT meteorite hit?
In the Chicxulub Crater in the Yucatan Peninsula. There are gravity anomalies.
What is the quartz evidence for KT extinction?
The other main piece of evidence for an extraterrestrial impact is the presence of shocked quartz (microscopic breaks), caused when quartz is placed under immense pressure. Found all over North America.
What is the microspherules evidence for KT extinction?
Evidence for the impact; when the meteorite hit the earth a lot of dust-sized debris rose, and the bigger pieces hit the earth again and were mini-meteorites. The medium chunks melted as they fell down towards the earth and froze in the last bit of the fall and so they froze in balls of glass. Thought to be evidence or meteorite impact - problem is that they are usually spherical structures from different periods/or contamination of insect eggs.
When was the Cenozoic?
Periods of Paleogene, Neogene (65 MYA - 0 MYA).
What is the world like in the middle eocene?
North America, South America, and Africa are now in familiar shapes. Asia is still weird, Europe is a chain of small islands (no Alps). NA and SA are not connected to each other (no central America).
What is the world like in the middle Miocene?
India has collided with Asia (Tibetan Plateau); Europe is weird still. NA and SA have almost met each other but there is still gaps. Glaciers have formed in Greenland, Hudson’s Bay is still dry land.
What is the world like 18,000 years ago?
The Last Glacial Maximum - large glaciers; NA and Europe and Asia are covered in massive ice sheets. Kilometres thick. Areas near the Yukon/Alaska border were not covered.
Australia was almost connected to Asia. Water level was so low that the Mediterranean Sea wasn’t connected to anything and almost dried up several times.
How long did it take for the dominant land vertebrates of the Late Cretaceous to be replaced after the KT extinction?
5-10 million years.
What happened before the land vertebrates were replaced?
During that time there were no large herbivores and there were very few predators of any size. The ones around are lizards, crocodiles, birds - things that survived the KT Extinction.
What was present around the end of the Paleocene?
There are several 4-5 tonne herbivorous mammals, which are of different ancestry on separate continents; there are large carnivorous birds (Terra birds) that were the main predators.
What happened to marine reptiles after the KT extinction?
No marine reptiles survived, and it wasn’t until the Eocene that animals came to fulfill those roles (whale eating fish).
What was the environment like during the Paleocene and Eocene?
The mean annual temperatures were high, and abundant precipitation fell, and tropical to semitropical forests covered much of North America.
Mammalian Orders by the Eocene.
Many mammalian orders that evolved during the Paleocene become extinct but of the several that first appeared during the Eocene only one has become extinct; by the Eocene time many of the mammalian orders existing now were present (e.g. ancestors of horses, camels, elephants, rhinos, whales, bats). Yet if we could go back for a visit we would not recognize most of these animals.