Trace no. 8   This is still another fake fossil. It is not marks from medusae although it may look like it.  Medusae are some of the oldes organisms on earth. Therefore it has been tempting to interpretate such structures in preCambrian rocks as biologically formed.
But this interpretation is problematic for several reasons: First of all 98% of a medusa is water, meaning that it quickly disappears after death. Secondly the marks that a medusa makes on the beach very rarely are preserved. Thirdly, the oldest medusae did not swim but were attached to the bottom. Fourthly, there are many other processes which may form concentric rings like these.

spor nr 8

This piece is  1 800 000 000 years old (1,8 billion years). It was found by Peter Haines in Proterozoic rocks in Australia.
It shows sand volcanoes formed when waterfilled sand is compacted under clay beds. The water become pressed up like a small volcanoe. It is possible that the form was preserved due to an algae mat.

Tilbage til
FOSSIL ART Time scale 
Sporfossiler i Danmark
Generel information Generelt om sporfossiler Front