Fossils in Building Material at Olympia, Greece

Many buildings at the ancient site of the Olympic games were built in a gray local stone that is packed with marine shell fossils. The Palaistra or wrestling school shown in the picture is a typical example. This stone is prone to weathering, so over time the shells are evident either as holes or as clearly profiled forms.

Where weathering has laid bare the shell casts, the scene is reminiscent of a shell-littered beach. Many shells were obviously fragmented before they were deposited and I saw no evidence of two cockle shells still being hinged together. It is likely that the shells were washed around for some time between the animal's death and the time of deposit. However, a fair number were fossilized in excellent condition.

These two pictures show the surface of building stone blocks. Cockles are by far the most common type of shell. They are easily recognized by the ribbing and half-heart shape. When both shells are hinged together, they look like a heart. Modern cockle species prefer mud or fine to medium sand into which they burrow. They are widely distributed around the globe in the intertidal zone and at varying depths of the subtidal zone. Cockles reproduce quickly because they are hermaphrodites, which is unusual for bivalves.

However, cockles are not the only type of shell found in building materials from Olympia. The following pictures show sections of the wall next to the door of the Byzantine church. Several gastropod shells are clearly visible.

The next picture shows a column section. Instead of exposing the shell casts, weathering has removed them from the stone matrix, giving the column a pock-marked appearance.

Olympia is located in a geological structure called the Pyrgos basin, which covers a large part of the NW Peloponnese. Its bedrock mostly consists of Plio-Pleistocene sediments with older Pliocene sediments cropping up over large sections-- not very old in geological terms (5 - 1.8 million years ago). The adjoining areas (and the entire central Peloponnese) are covered by older Mesozoic rocks.


I took the pictures in this page on June 4 & 5, 2005. No commercial/for profit use is permitted without my written permission. Please let me know if you plan to use these pictures for private or non-profit purposes and credit them properly.