Australia: The Land Where Time Began

A biography of the Australian continent 

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.

There are many, varied mountain chains in Europe, Africa and the Middle East, including the Betics, Atlas, Pyrenees, Alps, Apennines, Dinarides, Hellenides, Carpathians, Balkans, Taurus, Caucasus and Zagros mountains. The most recent orogenic phase (mountain building), the Alpine-Himalayan Orogeny, produced these mountain ranges plus the Himalayas. The closure of the Tethys Ocean was involved in the raising of all these mountain ranges, as well as the grinding of plates against each other along major suture zones. The movement of the plates is continuing as Arabia pushes against Iran, a new rift opening between the Gulf of Aden to the Dead Sea, while Turkey is sliding west into the Aegean Sea, and to the north of Egypt and Libya the seafloor is being subducted beneath Italy, Greece and Cyprus.

Sources & Further reading

Stow, Dorrik, 2010, Vanished Ocean; How Tethys Reshaped the World, Oxford University Press. 

 

 

Author: M. H. Monroe
Email:  admin@austhrutime.com
Last Updated 10/04/2012
 
Oceanography
 

 

Home
Journey Back Through Time
Geology
Biology
     Fauna
     Flora
Climate
Hydrology
Environment
Experience Australia
Aboriginal Australia
National Parks
Photo Galleries
Site Map
                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading