Geological development of Antarctica and paleontological evolution of Gondwana
On the world map
The Antarctic Peninsula is across the Strait of Drake from South America (Figure 1).
Figure 1 Location map of the Drake Strait
Read it in recent days
Geological Development in Antarctica and The Paleontological Evolution of Gondwana,
Learn that this place once existed
An ancient land bridge known as the Isthmus of Scotia.
Marsupials are through this
Migration from South America to Antarctica,
It then migrated from Antarctica to Australia.
This is the same as gondwanaland's
Geological history is closely related.
Formation of the ancient land of Gondwana
Dating back to the Cambrian Period 500 million years ago,
Current Africa, South America,
Antarctica, Australia,
New Zealand, India, Madagascar, etc
Both are part of the gondwana ancient land.
From the late Carboniferous to the Early Jurassic,
Global continental plates come together to form
Pangea (Figure 2).
Figure 2 Schematic diagram of Pancontinent
170 million years ago, the Pancontinent disintegrated into two parts,
To the north is Laurasia,
To the south is the gondwana ancient land.
At this point the North Atlantic Ocean began to crack.
By the late Paleocene,
The North Atlantic Ocean and the Arctic Ocean run through,
The Lauya Ancient Land was completely divided into
North America and Eurasia.
Decomposition of the continent of Gondwana
Gondwana Ancient Land
Cleavage begins in the Late Jurassic.
Early Cretaceous,
Antarctica has been separated from Africa,
Madagascar - India and Africa, Antarctica,
Australia separated and moved north,
The Indian Ocean began to form.
At the same time South America is separated from Africa,
In between, the South Atlantic Ocean was formed (Figure 3).
Figure 3 130 million years ago (Early Cretaceous) global continental plate rift
During the Late Cretaceous,
Madagascar separated from India 88 million years ago,
New Zealand separated from Antarctica 81 million years ago.
Australia's separation from Antarctica
It happened about 53 million years ago (Eocene).
South America and Antarctica are
The last land mass to split off in Gondwana.
From the Late Cretaceous to the Eocene,
Between South America and Antarctica
It is about 900 kilometers long and more than 100 kilometers wide
The Scotia Isthmus is connected.
29 million years ago (Oligocene)
South America and Antarctica are completely separated.
Glaciers and plants
Including Antarctica
Most of the ancient land of Gondwana,
From the Late Carboniferous to the Early Permian
Covered by glaciers.
From then on until the Eocene,
Antarctica's environment is suitable for the survival of animals and plants,
Water dragons, dinosaurs, tongues,
Artificial beech, silicified wood, etc
The discovery of fossils of plants and animals illustrates this.
Antarctica's Permian, Triassic, Neogene
There is a coal seam in the formation,
It reflects the widespread distribution of forests and swamps at that time
Warm and humid environment.
After the formation of the Drake Strait during the Oligocene,
The Pacific Ocean and the Atlantic Ocean are interconnected here,
Gradually formed a strong ocean current around Antarctica,
Since then, the Antarctic continent has been gradually covered with snow and ice.
The earliest marsupial fossils
The world's earliest marsupial fossil
Found in North America,
The geological age is the Early Cretaceous (110 million years ago).
Found in South America and Australia
The earliest marsupial fossils,
Geologically dated to the Late Cretaceous (70 million years ago)
and the early Eocene (50 million years ago).
In the late 1990s,
U.S. and Argentine Antarctic Expeditions
Near the Antarctic Peninsula
Seymour Island
Found marsupial fossils (Figure 4),
The geological age is the late Eocene (40 million years ago).
Figure 4 Southern hemisphere marsupial fossil origin
The origin of marsupials
Although there is currently controversy about the origin of marsupials,
But according to the existing fossil findings,
Experts in related fields believe
Marsupials are from southern South America
Enter Antarctica via the ancient land bridge of the Isthmus of Scotia,
It then migrated from Antarctica to Australia.
It is estimated that this migration occurred
60 million years ago to 55 million years ago.
It is also believed that marsupials originated in Australia.
It then migrated via Antarctica to South and North America,
But this view is not supported by existing fossil evidence.
After the dissolution of Pancontinental,
South and North America have long been separated by oceans.
3 million years ago due to the role of plate movement,
The Isthmus of Panama rises from the sea to connect South and North America,
Provides a migration channel for animals and plants.
Carnivores migrating from North America via the Isthmus of Panama to South America
These include saber-toothed tigers (extinct), jaguars, mountain lions, tiger cats, canines, etc.
As you can imagine,
These predators
Survival of marsupials to South America
There must have been a negative impact.
Australia has remained isolated for more than 50 million years.
Thus becoming a paradise for marsupials (Figure 5).
Figure 5 Kangaroos in Australia
bibliography
Chen Tingyu,Shen Yanbin,Zhao Yue,Ren Liudong. Geological Development of Antarctica and Paleontological Evolution of Gondwana[M].Beijing:The Commercial Press,2008.]
Shen Yanbin. Drifting Antarctica: Looking for evidence of continental drift[M].Nanjing:Jiangsu Science and Technology Press,2011.
[3] Where did Antarctica come from. WeChat public account: Planet Research Institute, 2018-12-29.