Lecture Twenty Seven - Cenozoic: The rise of Australia's Unique Fauna Flashcards
What was the Cenozoic (Cainozoic) Era made up of?
Quaternary period (1.8my-now):
- Holocene Epoch(100my-now).
- Pleistocene (1.8my-0.1my).
Neogene period (23-1.8my):
- Pliocene Epoch (5.3-1.8my).
- Miocene (23-5.3my).
Paleogene period (65.5my-23my):
- Oligocene (33.9my-23my).
- Eocene (55.8my-33.9my).
- Palarocene (65.5my-55.8my).
Australia breks way from Antarctic and drifts north, crossing climate zones.
What happened in the Eocene (55mya)?
The Eocene occured in the Paleogene period which occured in the Cenozoic Era.
Australia was still aprtly connected to Antarctica through Tazmania.
Warm and wet climate over most of Australia.
Deciduous forests replacing coniders (evergreens).
Dinosaurs gone (we think), mammals brgin to take over the world, flightless birds, horned turtles, snakes, crocodiles and frogs around.
What hapened in the Miocene (early and late)?
The Miocene occured in the Neogene period, which occured in the Cenozoic Era.
Early Mioene (20 mya):
Australia drifting norothwards and isolated from other continents.
Warm and wet climate over most of Australia - Inland still rainforest, and not desert.
Northern Australia is a luch rainforest, similar to Borneo or Amazon basin today.
Possums, koalas, kangaroos (including carnivours), snakes, lizards and frogs exist.
Bats migrate from Indonesia (first placental mammals in Aus).
Late Miocene (8 mya):
Australia beginning to collide with Asia, forming island arc (PNG).
Aus dries out, as polar ice sheets grow over Antarctica - this increases the amount of desert, and therefore the amount of ligth reflected off the Earth, this cools the planet.
Sea levels drop, exposing the Nullaebor Plain carbonates above sea level.
Rainforests draw back to coastal areas.
Megafauna - diprotodontids, hopping kangaroos, ‘thunder birds’ (Bullockornis).
What occured in the Pliocene (4mya)?
Australia is close to its present position, as has collided with South Asia.
Australia alternating between warm and wet, and drying out - oscillatory climate.
Eucalypts and wattle trees dominate forests.
Browsers replace grazers in teh Pliocene and Pleistocene.
Megafauna included:
Diprotodon - 1.7m at shoulder, 3m long, about a tonne heavy, largest marsupial ever.
Megalania - giant goanna, 5-7m long, 600kg.
What occured in the Pleistocene (1.8-0.1mya)?
Australia is very close to present position.
Global drop in sea levels, exposed continental shelves and allowed migration between PNG, Tazmania and mainland Aus.
Polar caps grow and diminish in rapid ycles - alternatees periods of wet and dry in Aus.
Grasslands enlarge, eukalypts mainly restricted to coasts.
Megafauna dominate.
Humans migrate into Aus between 100,000 and 65,000 years ago.
What occured in the Holocene (10,000ya).
Australia very close to rpesent day position.
Australia gets slightly wetter until about 5,000 years ago, and then dries out.
Fire stick burning used to ‘farm’ animals and plants by humans.
European settlers radically change vegitation nd fauna.
Megafauna mainly extinct, mass extinctions occuring in the recent due to human activity.
Explain the Antarctic circular current.
Transports 130million meters cubed per second.
Only current that circles the globe.
Transports heat from one ocean basin to another.
Isolates Antarctica and ensures that it is always cold because no warm currents can get to it.
What happened to all of Antarcticas life?
When seperated from Aus and Sounth America, it completely glaciated.
Almost all life went extinct, too far to swim or fly away from, so only those organisms that could adapt to the environment survived.
Explain the Sirius group rocks and the controversy around them.
Fossils of fresh water mollusc shells, fish, diatoms, plants and peat moss were found from 3 mya.
These imply that there was significant ice melting and sea level rise.
Then there were more diatoms found in poor condition, which were suggested to be from contamination (blown from else where on to Antarctica).
More recently again, more fossils were found of land animals and plants.
All fossils in situ, indicating temperature between 2 and 5 degrees C.
More diatoms, this time deep within rock.
Age obtianed was 3 mya.
The argument is still going on as to whether or not Antarctica melted 3mya.
