SUMMARY:
Researchers
found evidence
of rain forests
near the South Pole
90 million years ago,
suggesting the climate
had been very warm.
They discovered
evidence of a temperate
rainforest in the region,
such as would be found
in New Zealand today.
This was despite
a four-month long
polar night,
meaning
for a third
of every year
there was
no sunlight
at all.
Researchers conclude
that 90 million years ago
the Antarctic continent
was covered with dense
vegetation, there were
no land-ice masses
on the scale
of an ice sheet
in the
South Pole region,
and the
carbon dioxide
concentration
in the atmosphere
was far higher than
previously assumed
for the Cretaceous.
Lead author
Dr Johann Klages,
from the Alfred Wegener
Institute Helmholtz Centre
for Polar and Marine
Research, said:
"Before our study,
the general assumption was
that the global carbon dioxide
concentration in the Cretaceous
was roughly 1,000 ppm.
But in our model-based
experiments, it took
concentration levels
of 1,120 to 1,680 ppm
to reach the average
temperatures back then
in the Antarctic."
DETAILS:
A team
from the U.K.
and Germany
discovered
forest soil from the
Cretaceous period
within 900 km of the
South Pole.
Their analysis of the
preserved roots,
pollen and spores
shows that the world
at that time
was a lot warmer
than previously
thought.
The international team
was led by geoscientists
from the Alfred Wegener
Institute Helmholtz Centre
for Polar and Marine
Research in Germany
and included Imperial
College London
researchers too.
Their findings were
published in Nature.
Co-author Professor
Tina van de Flierdt,
from the Department
of Earth Science &
Engineering at Imperial,
said: "The preservation
of this 90-million-year-old
forest is exceptional,
but even more surprising
is the world it reveals.
Even during months
of darkness, swampy
temperate rain forests
were able to grow
close to the South Pole,
revealing an even warmer
climate than we expected."
The work also suggests
that the carbon dioxide
(CO2) levels in the
atmosphere were higher
than expected during
the mid-Cretaceous period,
115-80 million years ago,
challenging climate models
of the period.
The mid-Cretaceous
was the heyday of the
dinosaurs but was also
the warmest period
in the past 140 million
years, with temperatures
in the tropics as high as
35 degrees Celsius and
sea level 170 meters
higher than today.
The presence
of the forest
suggests average
temperatures were
around 12 degrees C.
and that there was
unlikely to be
an ice cap
at the South Pole
at the time.
The evidence is from
a core of sediment
drilled into the seabed
near the Pine Island
and Thwaites glaciers
in West Antarctica.
One section of the core,
that would have originally
been deposited on land,
caught the researchers'
attention with its
strange color.
The team CT-scanned
the section of the core
and discovered a dense
network of fossil roots,
so well preserved that
they could make out
individual cell structures.
The sample also contained
traces of pollen and spores
from plants, including the
first remnants of flowering
plants ever found at these
high Antarctic latitudes.
To reconstruct
the environment,
the team assessed
the climatic conditions
under which the plants'
modern descendants live.
They found that the
annual mean
air temperature
was around
12 degrees Celsius;
two degrees warmer
than the mean
temperature in
Germany today.
Average summer
temperatures were
about 19 degrees C.
Water temperatures
in the rivers and swamps
reached up to 20 degrees.
ANTARCTICA'S
GEOLOGY
East and West
Antarctica
are quite different.
East Antarctica
is much larger
and is an area
of continental
shield (or ‘craton’)
composed of
ancient igneous and
metamorphic rocks,
some exceeding
3 billion years old !
Overlying the ancient
rock are younger
sedimentary rocks.
Coal beds exposed
in the Transantarctic
Mountains formed
by the accumulation
of plant matter during
the Permian Period
( 290 to 245 million years ago) .
The geology of
West Antarctica
has much
in common
with the geology
of the Andes.
Subduction, volcanism,
and uplift of this region
occurred almost continuously,
until about 35 million years ago,
and ceased when the Antarctic
Peninsula and South America
finally separated to create
the Southern Ocean.