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4.2.7. Aye Formation - AYE

Authors: Bouckaert et al., 1968; Thorez et al., 1977.
Description: As pointed out by Bouckaert et al. (1968), the Esneux Fm passes laterally in the southern part of the Dinant Synclinorium (i.e. in a more offshore position) to the Aye Fm (former name: Aye shales or schists).  The dominant lithology is that of greenish shale with alternating interbedded greenish argillaceous platy siltstone beds and lenticular (some cm thick) fine-grained sandstones and siltstones.  Bioturbation is important.  Brachiopods accumulations and limestone beds are locally frequent.  The overall paleobathymetry for the Esneux and Aye Fms is that of a subtidal wave-influenced environment.  Cross-bedding structures are related to storm current origin (tempestite).
Stratotype: area of Houyet and Aye.
Area: South of the Dinant Synclinorium; north of the Philippeville Tectonic Unit.
Thickness:  at least 140 m in the Silenrieux area; 220 m in the Hermeton valley.
Age: Base of the Middle Famennian (Fa2a).  P. rhomboideaconodont zone.