Tethys is a geo syncline!!

A geosyncline is a part of the earth's crust that is prone to downward warping during a long span of geologic time. It is a large depression that contains very thick deposits.

a very large depression on the earths surface, like trough, which contains mounds of sedimentary and volcanic rocks.

Dwight Eugene Mayo has written:

'The development of the idea of the geosyncline' -- subject(s): Geosynclines

A geosyncline is a belt of sedimentary deposits that accumulate within the ocean along the margin of a continent - on the continental shelf and slope.