A keystone in a changing world - Antarctica: Global Science from a Frozen Continent - page 65

Antarctic forests, along with the monkey puzzle conifer, Araucaria . Mean annual
temperatures had dropped to around 10ºC with winter temperatures below freezing.
The onset of glaciation and cold climates led to the demise of Antarctic vegetation.
Plant macrofossils are rare from rocks younger than 40million years old but fossil
pollen shows that tundra vegetation was present with small bushes of Nothofagus ,
mosses and rare conifers. In the Beardmore Glacier region of the Transantarctic
Mountains, a unique

flora of dwarf Nothofagus bushes, cushion plants and mosses is
preserved sandwiched between glacial deposits. Preserved in their growth position,
these plants grew only 300miles from the South Pole and indicate a short burst of
climatic warmth and glacial retreat during the icehouse world. These fossils heralded
the end of Antarctica s ancient forest as the glacial landscape took over. Another

amazing fossil horizon was discovered within the Victoria Land Dry Valleys in 2000.
Soft organic material has turned out to be desiccated slabs of an ancient 14million
year old lake bed that has preserved freeze dried aquatic mosses, pea-sized
freshwater ostracods, thick deposits of diatoms, pollen leaves and twigs of southern
beech, aquatic quillworth plants and fragments of insects including a species of
weevil. These fossils paint a picture of an alpine lake damned behind glacial
moraines, surrounded by tundra and weather beaten southern beech shrubs
14million years ago with temperatures at least 20ºC warmer than today. It is very
likely that this part of Antarctica has remained cold since this time as if this deposit
had become warmer and wetter, microbes would have mined these deposits as
carbon sources.

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A changing world

Geological exploration in Antarctica has provided a unique record of how our
Earth System functions, how it has evolved through time and how the continents
amalgamated and combined in different con gurations through geological time.

The unusual position that Antarctica occupied as the central keystone of Gondwana
enabled Antarctic geologists to provide crucial evidence in support of the theory
of plate tectonics, to contribute to global debates surrounding the breakup and
disintegration of large continents, to understand how our climate has changed
and how plants and animals have evolved as the continents drifted through different
climatic belts. Temporary land bridges in uenced the migration and evolution

of new species and constrained the global distribution of the Earth s species.

Our investigations of the Antarctic rock record have allowed us to investigate
and understand the interaction between the Earth

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s biosphere, atmosphere and
lithosphere and how those interactions have evolved and functioned through time.
The data provide a valuable benchmark against which we can monitor and predict
future changes due to human-induced increases in atmospheric greenhouse gases.

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