A Chalk-a-licious field trip to the Danish East coast

In the last weekend of September  AmsterdamPG participated in a field trip  to Denmark organised by PGK  to visit the chalk deposits on the eastern coast of Denmark. Dr. Kresten Anderskouv, Prof.  Lars Stemmerick and Florian Smit of  the DHRTC guided a group of 30 professionals along the Danish coast to see some beautiful and quite remarkable outcrops.

Bryozoan mounds at Stevns Klint
The trip started with  a visit to the UNESCO heritage site  of Stevns Klint, part of the Danish Chalk cliffs. Along the beach of this cliff the Bryozoan mounds were clearly visible. At first sight the whole stratigraphy seemed to be overturned due to a sharp discordance contrast at eye level. However, what we were looking at were Bryozoan mounds growing sideways over adjacent sediments. As these low-angle mounds reach sizes of ten to hundreds of meters, they are not immediately recognizable as such when standing directly in front of them, let alone having only some core material available.

The Bryozoans form the main structure of the top of the Cretaceous stratigraphy in this region and are alternated with bands of sharply contrasting dark flint. The flint really helps visualizing the structure in the chalk, as the chalk itself looks like a homogeneous white mass. Further down in the stratigraphy the amount of flint appears to thin down, which seems to be related to increased water depth. Good to keep in mind if you consider drilling in this reservoir.

Stevnsfortet
We also visited  the premises of an old Cold War bunker. Though it wasn’t  directly apparent how the bunker was associated with chalk geology, this soon became clear when entering the subsurface corridors. The hallways give a very nice 3D image of the Chalk. It also becomes evident that the material is quite strong, as no additional support is needed to keep the corridors from collapsing.

Faxe Quarry

The trip ended  in the Faxe Quarry, where it was possible to obtain your very own beautiful Chalk specimen. Though a lot of material was also available along the coast, the available corrals in the quarry were of top quality. Very interesting to know is that a lot of the observed porosity is actually the inverse of the original coral: the original coral is dissolved and accordingly redeposited in the space between the coral. This still leaves some remarkable structures.

All in all the field trip was a very enjoyable and instructive trip. Once again it showed that it really helps to get your hand on the rock once in a while.

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