Geoparque Unesco

The Paleozoic Era

The Hercynian geologic period starts with Sobrarbe submerged by the sea. The sediments of carbonates (Devonian) and lutites (Silurian) prevail, with levels of detritic sediments increasing during the Carboniferous, around 300 million years ago, as a consequence of the Hercynian orogeny, until the end of the period. The Pangea formation brought about the collision of tectonic plates and the rising of large mountain ranges, higher than the Pyrenees, devastated at the end of the Paleozoic era.

During the sedimentation stage of the Hercynian cycle, huge amounts of sediments were stored at the bottom of the sea or by its shores. Millions of years later, they stayed deeply buried in the subsoil and were transformed into sedimentary rocks. When the cycle came to an end, some magma (batholiths) was ejected from deep in the Earth being stopped by these rocks from reaching the surface. The pressure and the heat (650ºC-1200ºF) endured by the rocks due to the magma proximity caused physical and chemical changes transforming them into metamorphic rocks (clay turned into slate, sandstone turned into quartzite and schist, limestone turned into marble, etc). Fossils from this period are rare, since this process destroyed most of them.

The Earth, 420 million years ago.

Granite mountains in the north of Sobrarbe are part of those batholiths. Hot water springs in the Pyrenees are a sign that batholiths are still heating the water flowing through their chasms.

Paleozoic rocks:

Metamorphism also had much to do with mineral ore formation and the mineral deposits that were exploited in past centuries

Among the most remarkable events in Earth's history we find: the first fish, the Ordovician-Silurian Glaciation, the first earth plants, the first insects, the Pangea formation and the Permian extinction event.

Samples of the most ancient rocks in Sobrarbe.

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