Sedimentary rocks near Heraklion preserve traces of an ancient sea, geological record shows

Rock formations in the area of Agia Irini, in Spilia south of Heraklion, contain marine fossils that show the region was once covered by sea, according to geological records cited by Cretaone. The rocks belong to a category known as Neogene sedimentary formations, laid down in what was then a marine environment rather than the dry land seen today.

Marine fossils preserved in central Crete’s rock layers

In such rock formations across central Crete, marine fossils have been recorded that indicate the environment in which they formed was very different from today’s landscape. Shells and other marine organisms can be preserved within sediment layers and, millions of years later, serve as a kind of natural record of past conditions.

How did an ancient sea end up on dry land?

The sea itself did not physically move as a body of water — the land did. Crete sits in one of the most geologically active regions of the Mediterranean, where the convergence of tectonic plates, combined with uplift and subsidence over millions of years, has reshaped the island. Areas that once formed the sea floor were gradually uplifted and became dry land.

Fossils act as a record of past environments

This process is what makes the rock formations of interest to researchers. A small fossilized shell is not simply an unusual shape embedded in stone; it can indicate the environmental conditions that existed when that particular rock layer formed. Geologists study such fossils together with the composition and position of the surrounding rock to reconstruct how a given area evolved over time.

Crete’s current landscape represents only the most recent stage of a much longer geological history, with sections of today’s terrain having passed through different geological phases before taking their present form — a history recorded in the island’s rock layers rather than only at its archaeological sites. A similar process has been documented at Mochlos islet, where researchers say sea-level rise once separated the site from the mainland. Readers interested in exploring more of the island’s geological and natural features can find further background among places in Crete.