BYBADAL DUTT MATHUR

EVOLUTION OF TETHYS SEA

INTRODUCTION Tethys Sea, former tropical body of salt water that

separated the supercontinent of Laurasia in the north from Gondwana in the south during much of the Mesozoic Era (251 to 65.5 million years ago). Laurasia consisted of what are now North America and the portion of Eurasia north of the Alpine-Himalayan mountain ranges, while Gondwana consisted of present-day South America, Africa, peninsular India, Australia, Antarctica, and those Eurasian regions south of the Alpine-Himalayan chain. These mountains were created by continental collisions that eventually eliminated the sea.

Tethys was named in 1893, by the Austrian geologist Eduard Suess, after the sister and consort of Oceanus, the ancient Greek god of the ocean.

TYPES OF TETHYS SEA

At least two Tethyan seas successively occupied the area between Laurasia and Gondwana during the Mesozoic Era.

1. PALEO TETHYS SEA

2. NEO TETHYS SEA

PALEO TETHYS SEAPaleo (Old) Tethys Sea, was created when all landmasses

converged to form the supercontinent of Pangea about 320 million years ago, late in the Paleozoic Era. During the Permian and Triassic periods (approximately 300 to 200 million years ago), Paleo Tethys formed an eastward-opening oceanic embayment of Pangea in what is now the Mediterranean region. This ocean was eliminated when a strip of continental material (known as the Cimmerian continent) detached from northern Gondwana and rotated northward, eventually colliding with the southern margin of Laurasia during the Early Jurassic Epoch (some 180 million years ago). Evidence of the Paleo Tethys Sea is preserved in marine sediments now incorporated into mountain ranges that stretch from northern Turkey through Transcaucasia (the Caucasus and the Pamirs), northern Iran and Afghanistan, northern Tibet (Kunlun Mountains), and China and Indochina.

NEO TETHYS SEAThe Neo (New, or Younger) Tethys Sea, commonly referred

to simply as Tethys or the Tethys Sea, began forming in the wake of the rotating Cimmerian continent during the earliest part of the Mesozoic Era. During the Jurassic the breakup of Pangea into Laurasia to the north and Gondwana to the south resulted in a gradual opening of Tethys into a dominant marine seaway of the Mesozoic. A large volume of warm water flowed westward between the continents and connected the major oceans, most likely playing a large role in the Earth’s heat transport and climate control. During times of major increases in sea level, the Tethyan seaway expanded and merged with seaways that flowed to the north, as indicated by fossil evidence of mixed Tethyan tropical faunas and more-temperate northern faunas.

Figure showing Plaeo-Tethys and Tethys Ocean

Clousure Of Tethys SeaTethys closed during the Cenozoic Era about 50

million years ago when continental fragments of Gondwana—India, Arabia, and Apulia (consisting of parts of Italy, the Balkan states, Greece, and Turkey)—finally collided with the rest of Eurasia. The result was the creation of the modern Alpine-Himalayan ranges, which extend from Spain (the Pyrenees) and northwest Africa (the Atlas) along the northern margin of the Mediterranean Sea (the Alps and Carpathians) into southern Asia (the Himalayas) and then to Indonesia. Remnants of the Tethys Sea remain today as the Mediterranean, Black, Caspian, and Aral seas.

Effect Of The Evolution Of Tethys Sea

An important effect of the evolution of the Tethys Sea was the formation of the giant petroleum basins of North Africa and the Middle East, first by providing basins in which organic material could accumulate and then by providing structural and thermal conditions that allowed hydrocarbons to mature.