Tethys Sea

Tethys Sea, ancient ocean. By about 300 million years ago, towards the end of the Palaeozoic Era, all the landmasses had coalesced to form a single large continent, known as Pangaea. This landmass was crescentic in shape and a large wedge-shaped area of ocean separated the southern continental masses of Gondwana (South America, Africa, India, Australia) from the northern continental masses of Laurasia (North America, Europe, former Soviet Union, China). It is this ancient oceanic region that is termed Tethys. In Greek mythology, Tethys, a Titan, was the daughter of Uranus, god of Heaven, and Gaea, goddess of Earth, and wife of her brother, Oceanus.

Starting in the latest Permian or Triassic Periods, rifting between Africa and Europe caused the Tethyan ocean to start spreading westwards, creating an arm of the ocean that extended between Africa and Europe. By late in the Jurassic Period, about 150 million years ago, the Tethyan seaway attained its greatest extent and Africa and Europe were more or less fully separated by ocean, with the seaway reaching as far west as the area of the present-day Caribbean. Ultimately, during the Early Cretaceous, an unbroken equatorial seaway was created that enabled wide dispersal of marine fauna and flora.

Tethys acted as a collecting basin for sediments during the Mesozoic Era, and deep-water limestones and chalks built up along the seaway’s margins. However, the break-up of Pangaea also led to parts of the northern margin of Gondwana becoming tectonically separated (see Plate Tectonics). Continental drift caused these strips of land to move across Tethys until they eventually collided into the Laurasian landmass. The entire Indian peninsula, for example, was originally part of Gondwana, but became separated by rifting from Antarctica and Africa in the Cretaceous and transported northwards by plate tectonic movements. Sediments that were originally deposited along the margins of Tethys became caught up in the subsequent collision and were uplifted in the post-collision deformation, creating some of the world’s youngest and highest fold mountains. Collision of the Indian subcontinent into Eurasia was responsible for creating the Himalaya about 35 million years ago. Further west, and a little later (about 14 to 18 million years ago), Africa and Arabia moved against Europe with much the same effect, creating the Alps and the mountains of Turkey, Iran, and Afghanistan that today connect with the Himalaya. Thus along this Alpine-Himalayan belt, sections of rock that once formed the seabed of the Tethys Sea are to be found. About 20 million years ago there was still a long northern arm of the Tethyan seaway that extended deep into Asia. This seaway became isolated about 14 million years ago forming the Paratethys sea, and ultimately was broken up into a series of isolated basins. Today the Caspian, Black, and Aral seas represent the vestiges of the great Tethyan seaway.