Sponge reef

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The rock formations at the Danube Gorge near Beuron were created from sponge reefs

A sponge reef is understood to be a reef built up by pebble sponges over very long periods of time. Particularly large fossil sponge reefs can be found, for example, on the Swabian Alb in the mass limestone of the White Jura . At the Danube breakthrough near Beuron (Baden-Württemberg), the towering Jurassic rocks carved out by erosion show the fossil sponge reef formation particularly impressively.

The Amazon reef ( Portuguese Recife Amazonas ) is a large-scale calcareous algae and sponge reef off the coast of northern Brazil and French Guiana . It is one of the largest reef systems in the world with a length of 970 km and an area of ​​about 9500 km².