Reconstruction of past landscapes.

 

Analysis of the Devonian (Frasnian) platform from Belgium: A multi-faceted approach for basin evolution reconstruction.

2012

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Da Silva, AC., Boulvain, F.

Basin Research, 24, 338-356

Understanding past landscapes, their evolution, and environmental changes are important components of geology. In this work, we propose to reconstruct the marin landscapes and the coast of past Belgium, ... 375 million years ago, during the Frasnian period (Upper Devonian).

At this time, Belgium was located at about thirty degrees of southern latitude, it was covered with a sea which deepens towards the south. In combination with a tropical climate, this situation allowed the development of many reefs.
 

In this work, we have shown that when sedimentation begins at Frasnian, the marine basin (or carbonate platform) shows a very important relief with areas under a deep sea to the south and other areas that emerged to the north. The sediments and fossils that settle there are very different depending on where you are. Deep underwater reefs are deposited in the south of Belgium (Frasnes, Philippeville, etc.) with shallow deposits in the north or no deposit at all. The oceanic circulation around this Belgian sea is good, with a sea open to other marine basins.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In the middle part of the Frasnian, the conditions change, first of all, the structure of the platform flattens out and becomes simpler, there is no real difference between the different zones anymore, the sediments and the fossils become very homogeneous. Ocean circulation decreases and signs of stagnant water appear. This could be related to the development of a large reef barrier reef (such as the Great Barrier reef in Australia) that would have "close" our sea. We also note that the water depth is decreasing and that the lagoon areas are developing everywhere on the platform, homogeneously.

At Upper Frasnian, conditions become more open again, circulation with other ocean basins is restored, and sea level increases. We are getting closer to the major Frasnian-Famennian crisis, one of the major crises that has affected our planet (see Time matters and when planets influence the climate).