Facies distribution on a carbonate ramp controlled by underground relief and subsidence (Late Eocene of the eastern Alpine Foreland Basin)

 

14. Reconstruction - Stage 3

The rising sea level, caused by continuous subsidence of the foreland, reaches the northern-most part of the depositional basin. Terrigenous input only occurs along the coast, high zones are completely flooded. The rate of carbonate sedimentation can keep up with rising sea level in the northern area. Fragmentation of coralline algae is low. Crustose frameworks are restricted to the swells. The peyssonneliacean limestones reflect the occurrence of muddy areas deeper than in stages 1 and 2. In contrast to the algal limestones of the northern area, sedimentation rate of the southern area is too low to keep up with the rising sea level. Some glauconite is formed. The Bryozoa Facies suggests an environment below the photic zone. Coralline detritus originate from the northern area and can be interpreted as grain flows reworking bryozoans.

The dominance of bryozoans can be alternatively interpreted by eutrophication. The eutrophication of the environment caused a high water turbidity and did not allow the occurrence of light-dependent organisms. In this case, the overlying algal-dominated facies may represent a progradation of (par)autochthonous algal sediments.

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