Urban fossils are the remains of extinct organisms that have been preserved on construction stones.
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Marine fossils on the streets of Amsterdam

The city of Amsterdam hides very good examples of urban fossils on building walls and the pavements of streets and squares. As Annemieke van Roekel describes in her book «Discover Fossils in Downtown Amsterdam», the Carboniferous limestone known as "bluestone" has been used for centuries as a construction stone on pavements, façades, staircases, windowsills, etc. Since this rock is very rich in marine fauna, you can find interesting urban fossils on a walk through the city's historic centre.
Two varieties of "bluestone" can be found on the streets of Amsterdam's city centre. Large blocks and slabs of this stone that have been traditionally used in the oldest buildings of the city have been quarried in The Ardennes, Belgium. This Carboniferous limestone is very rich in fossil remains of some of some the main marine groups of that period, such as crinoids (sea lilies) and brachiopods. Crinoid fragments are very common in Belgium "bluestone", as can be seen in many buildings of Amsterdam' city centre.

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Brachiopod (left) and coral colony (right) on the pavement of a sidewalk

Over the last few decades, the city of Amsterdam has renewed the paving stones of many cities with Irish "bluestone". Although the Irish "bluestone" is about ten million years younger that the Belgium "bluestone", it was formed in the same shallow, tropical sea, therefore they share many features. The fossil content of the Irish "bluestone" is very similar to the older Belgium limestone, although the former usually preserves a larger proportion of brachiopods and corals. One of the most characteristic features of the Irish "bluestone" is the ubiquitous presence of Productive brachiopods. These marine shells are relatively large, some of them more than 10 cm long.

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Irish "bluestone" with Productida brachiopods


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Irish "bluestone" with Productida brachiopods

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Longitudinal cross section of a gastropod in a "bluestone"

Special thanks to Annemieke van Roekel for the information and photographs of her book «Discover Fossils in Downtown Amsterdam»and web site "Shell banks in the city". For more information on Amsterdam's urban fossils, visit www.geokids.nl and www.amsterdamfossils.com.

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