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| Tethys Ocean |
Stretching from what is now the Mediterranean to the Indian Ocean, the Tethys existed from the late Paleozoic through the early Cenozoic, roughly 250 to 50 million years ago.
The concept of this long-lost ocean was first proposed in 1893 by Austrian geologist Eduard Suess, one of the founders of modern geology. While studying the distribution of marine fossils in rocks found high in mountain ranges such as the Alps and Himalayas, Suess realized that these fossils—corals, ammonites, and foraminifera—must once have lived in a vast tropical sea.
His revolutionary conclusion: the mountains had been uplifted from the floor of an ancient ocean that no longer existed. He named this vanished sea the Tethys, after the Greek sea goddess and wife of Oceanus.
Evidence for the Tethys Ocean comes from both geology and fossil assemblages. Layers of marine limestone rich in Nummulites, ammonites, and other marine fossils are found across Europe, North Africa, and southern Asia—often thousands of meters above current sea level.
These rocks record an ocean teeming with life during the Mesozoic and early Cenozoic, later compressed and folded as the African, Indian, and Eurasian plates collided to form the Alps, the Himalayas, and the Zagros Mountains.
Its tropical lagoons once hosted coral reefs, sea urchins, mollusks, and the foraminifera that would later become Nummulites. As these tiny organisms lived, died, and settled onto the seafloor, their calcium carbonate shells accumulated in thick beds of lime mud. Over millions of years, these sediments hardened into the fossil-rich Eocene limestones that now form much of Egypt’s geology—including the very stone quarried for the pyramids of Giza.
Today, the remnants of the Tethys survive as the Mediterranean, Black, Caspian, and Aral Seas, but its story lives on in every fossil-bearing limestone block of the Great Pyramid—a geological time capsule of an ocean that vanished long before humankind emerged.
