ENIGMATIC TRACE FOSSILS

Life is tougher in the depths. It is pitch black and nutrients are scarce, but the flysch surprises us in mysterious ways.

Its layers are full of the trace fossils of organisms that moved through the seabed sediment forming tunnels and tracks, some with very distinctive and enigmatic shapes. They are called ichnofossils and they show us how certain species behaved in order to survive on the deep sea floor by filtering sediments, making tunnels or creating traps.

Ichnofossils

The Geoparkea flysch is a key global site for the study of deep-sea trace fossils. Over 40 different ichnofossils have been discovered here, some of them exceptional, and such enigmatic trace fossils as Rotundusichnium zumayensis were first described here and later found in other parts of the world.

Saerichnites abruptus

This is the largest and best-preserved recorded sample in the world. These are shallow tunnels that have been dug by organisms in the sediment, with intermittent vertical burrows on one side or the other, running towards the surface.

Paleodictyon 

This is one of the most mysterious trace fossils due to its perfect hexagonal shape. It has been found on the seabed for over 500 million years and is still there today. It can serve as a trap to “cultivate” bacteria or trap food. 

Spirorhaphe involuta 

Spiral trace fossils. The organism pierced the sediment in a spiral motion to feed itself, in a back-and-forth movement.

Zoophycus 

This is a feeding and digging tunnel with a spiral shape similar to a corkscrew. It is made with sweeping intricate movements by a colony that lived within the marine sediment.

Rotundusichnium zumayensis

An enigmatic trace fossil formed by narrow concentric rings that are difficult to interpret. This is one of the jewels in the crown and is very difficult to find, as it erodes easily. It was discovered and described for the first time in Zumaia by Joaquín Gomez de Llarena in 1946.

Chondrites 

A branching trace fossil with a complex algae-like pattern. It is made up of small feeding burrows with a distinctive feature: the organism never crosses any burrows that have previously been made. 

Helminthorhaphe 

Trace fossil with a meandering pattern. It is believed to be a trace fossil that has been left by an annelid that was feeding by filtering the sediment.

Scolicia

These are one of the most common trace fossils in the flysch. They are formed by the grazing activity of an echinoid that is still found today in the temperate seas of Southeast Asia. The replica displayed on the stairs is an exceptional specimen.