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Australia: The Land Where Time Began |
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The Belt of Tethyan ophiolites According to the author3 some slivers of
the floor of the Tethys Ocean have been thrust to very great heights,
such as the summit of Mount Makalu, an 8500 m high mountain on the
border of Nepal and Tibet, a neighbour of Everest, where the author3
suggests is a section of Tethys ocean floor, making it the highest
ophiolites in the world. He also suggests oceanic sediment from the
Tethys Ocean have been pushed still higher, saying there is bedded rock
that is barely visible through the snow cover near the top of Mount
Everest. The line of ultimate closure of the Tethys Ocean is marked by a
string of ophiolites that have been recorded along the High Himalaya,
together with heir seafloor sediments. Because of their great height it
is very difficult to study them closely. According to the author3 the belt of
Tethyan ophiolites can be seen to the east of Ladakh and Karakoram
Himalaya. They were the same green-black serpentines, some gabbros and
pillow lava basalts that were scattered in a typically chaotic mélange.
The same belt passes from Kashmir south through Pakistan and across the
Makran-Zagros Mountains Ranges in Iran. There is an almost straight
suture line here that stretches across the Middle East marking where the
2 plates collided, slivers of ophiolites and mélange escaping to the
surface. The zone becomes considerably broader as it passes through
Turkey, Syria and Cyprus, and on into Greece and Italy, eventually
extending to the Rhonda Ophiolite of south-eastern Spain. There are
hundreds of ophiolites marking the passage of the Tethys Ocean. From
mountain to dust The ocean floor of the Tethys Ocean is represented
by an ophiolite belt and the organisms that grew around seafloor vents.
The progressive closure of the ocean over tens of millions of years
resulted in a system of mountain chains running broadly east-west and
the ophiolite belt and fossilised vent communities are mostly part of
this system. What was originally subduction of oceanic crust became a
collision of continents. It has been possible to reconstruct much of the
history of the Tethys Ocean by studying the sediments that have not been
changed by the mountain building episode, as all kinds of Tethyan
sediments of various ages have been caught up in these orogenic events. The story of closure and uplift in the
Mediterranean is even more complicated than that of the Himalayas. The
author3 suggests a swarm of microcontinents appear to have
broken away from the leading edge of the African Plate as it approached
and pushed north to Europe and the Middle East crashed into central
Asia. The jigsaw puzzle of mountain ranges and remnant basins in the
whole Mediterranean region that make it one of the most complex on
Earth, results from the twists and turns of the microcontinents that
broke from the leading edge of the plate, as well as temporary spreading
centres, volcanoes, and abandoned trenches. Stow, Dorrik, 2010, Vanished Ocean; How Tethys Reshaped the World, Oxford University Press.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |