Late Frasnian phillipsastreid biostromes in Belgium
Poty, E.; Chevalier, E. (2007). Late Frasnian phillipsastreid biostromes in Belgium, in: Álvaro, J.J. et al. (Ed.) Palaeozoic reefs and bioaccumulations: climatic and evolutionary controls. Geological Society Special Publication, 275: pp. 143-161. https://dx.doi.org/10.1144/GSL.SP.2007.275.01.10 In: Álvaro, J.J. et al. (2007). Palaeozoic reefs and bioaccumulations: Climatic and evolutionary controls. Geological Society Special Publication, 275. Geological Society: London. ISBN 978-1-86239-221-2. viii, 291 pp., more In: Hartley, A.J. et al. (Ed.) Geological Society Special Publication. Geological Society of London: Oxford; London; Edinburgh; Boston, Mass.; Carlton, Vic.. ISSN 0305-8719; e-ISSN 2041-4927, more |
| Authors | | Top | - Poty, E., more
- Chevalier, E.
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| Abstract | In the Belgian Namur Dinant Basin the boundary between the Lustin Formation and the Aisemont Formation (in the Lower rhenana conodont Biozone) corresponds to a fall followed by a rise in sea level, leading to the first recorded late Frasnian coral crisis. The Aisemont Formation records a transgressive-regressive cycle. Prior to the crisis most of the colonial rugose corals were members of the Family Disphyllidae, but these were largely replaced by corals belonging to the Phillipsastraeidae. Among these Frechastraea colonized all environments of the basin and was the main constructor of a biostromal reef in its northern-most proximal area, in the fair-weather wave zone. Corals did not encrust each other and therefore were not firmly attached, but they hug tightly the substrate (a dead coral colony) and rest closely on it to resist to the turbulence of waves. During the Silurian and Devonian, up until the late Frasman crisis, shallow-water reefs in turbulent water were usually built by encrusting stromatoporoids, whereas rugose corals were restricted to waters of lower energy. Indeed, they were unable to encrust substrates, unlike stromatoporoids and post-Palaeozoic scleractinians, and to live in turbulent habitats. In Belgium argillaceous sedimentation prevented the development of stromatoporoids and provided an opportunity for the corals to colonize empty niches and to construct biostromes in relatively high-energy environments. At the same time Alveolites and stromatoporoids were dominant in a mid-proximal environment below the fair-weather wave base, but within the storm wave zone, where they also constructed biostromes. |
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