|A microbe-bryozoan reef from the middle Visean of the Namur Syncline (Enginoul quarry)|
Chevalier, E.; Aretz, M. (2005). A microbe-bryozoan reef from the middle Visean of the Namur Syncline (Enginoul quarry). Geol. Belg. 8(1-2): 109-119
In: Geologica Belgica. Geologica Belgica: Brussels . ISSN 1374-8505; e-ISSN 2034-1954
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A microbe-bryozoan patch-reef was temporarily exposed in the Lives Formation (middle Visean) at the Engihoul Quarry, southern limb of the Namur syncline. It developed within the Corphalie Member during the transition from bioclastic to stromatolitic facies. Reef formation is the result of a complex meshwork of calcified microbes, which formed complex layers which resemble “Osagia”-biocenose and individual columnar aggregates, fenestellid bryozoans, and early cements. Reef growth began on a hard-substrate provided by brachiopods and microbial crusts. Brachiopods (Composita sp.) are locally abundant in the reef facies, and contributed substantial firm ground for encrustation. Reef growth was controlled mainly by the abundance of fenestellid bryozoans. Their presence indicates reef formation during normal marine conditions. The reef developed in a high-energy area of the inner shelf. Reef growth probably stopped with the establishment of a peloidal mudstone facies, eventually indicating hypersaline conditions. The Engihoul reef is similar to Bomel reefs (also in the Lives Formation). All are the same age and developed in the transitional phase of the Corphalie Member, but minor differences in the individual reef fauna occur. The transitional phase of the Corphalie Member is an important horizon for reef formation with clear independence from other reef forming episodes within the Belgian Dinantian succession.