Estonian Fossils part III: The Pakri Peninsula

Pakri is a cliff area in northern Estonia. It has a lighthouse that is easily reached by road and is a good place to watch the sunset. Before reaching the lighthouse, there is an access with stairs to go down to the beach. There you can find the stones that have been dislodged and left visible.

Pakri cliffs, in Paldiski, Estonia. The fragments that break off make available samples of what each layer contains.
Pakri cliffs, in Paldiski, Estonia. The fragments that break off make available samples of what each layer contains.
Pakri cliffs, in Paldiski, Estonia. Detail of how the ground is fractured.
Pakri cliffs, in Paldiski, Estonia. Detail of how the ground is fractured.

In Pakri, in addition to the typical fossils that are easy to see in Estonia, there are a large number and variety of other different and mysterious types of fossils.
You can find more about fossils in Estonia in Estonian Fossils part I and Estonian Fossils part II: the rubble.

Although worn by the action of the water, remains of trilobite fossils can be found among the stones of the beach next to the sea. Pakri cliffs, in Paldiski, Estonia.
Although worn by the action of the water, remains of trilobite fossils can be found among the stones of the beach next to the sea. Pakri cliffs, in Paldiski, Estonia.

Among the most curious you can find:

  • Receptacle
  • Ripple marks
  • Rock spheres

What are each of them?

Receptacles

They have long been a mystery. Both its origin and its habitat are the subject of disagreements in the scientific community. What there is agreement on is that they belong to the Ordovician period (those found in Estonia), and that they can be found on all continents except Antarctica.

Its structure is reminiscent of that of the sunflower and that is why it has sometimes been called “sunflower coral.” They have a “double spiral radiating pattern.” And they are medium in size.

More info:
https://en.wikipedia.org/wiki/Receptaculites

Ripple marks

They are the result of sedimentation agitated by a current of water, and when they are fossilized like these they are also evidence that in a very distant period in time that area was submerged under water.

Ripple marks. Pakri cliffs, in Paldiski, Estonia.
Ripple marks. Pakri cliffs, in Paldiski, Estonia.

More info:
https://en.wikipedia.org/wiki/Ripple_marks

Rock spheres

I have not been able to find much information about them, only that it is a layer of pyritized sandstone in which these pebbles are found. If you have more information about what it is, don’t hesitate to tell me.

Reference link:
https://geoloogia.info/en/file/14517/