Revised stratigraphy of the Eifelian (Middle Devonian) of southern Belgium: sequence stratigraphy, global events, reef development and basin structuration

Abstract

The Eifelian lithostratigraphic succession of southern Belgium is here revised based on new field investigations and reconsideration of biostratigraphic data. The Couvin Formation is divided into four members: the Villers-la-Tour Member recorded the onset of stromatoporoid biostromes, the Petigny Member is a dark fine-grained limestone that recorded the Choteč event, the Cul d'Efer Member is dominated by stromatoporoid-coral biostromes. These first three members were previously united in the Foulerie Member and correspond to the transgressive and highstand system tracts of the Middle Devonian 3 rd -order sequence MD1. The argillaceous and bioclastic successive units of the Abîme Member recorded the sequence MD2. Laterally, this sequence is only composed of siliciclastic deposits of the Vieux Moulin, Station and Cimetière members of the Jemelle Formation. The highstand system tract is the newly introduced carbonate Vierves Member. Large bioherms, newly described as the Wancennes Formation, recorded the first two sequences MD1 and MD2. A major sequence boundary caps the Couvin Formation and is overlaid by the transgressive and diachronous Chavées Member of the Jemelle Formation with a depositional gap increasing eastwards. The highstand system tract of sequence MD3 is recorded in the bioherms of the Tienne Sainte-Anne Member (upper part of the Jemelle Formation), also capped by a sequence boundary. These bioherms probably acted as highs around which the sandy deposits of the Lomme Formation accumulated as lowstand system tract of sequence MD4. The Hanonet Formation and its crinoidal Wellin Member form the transgressive system tracts of sequence MD4 that terminates in the bioclastic and biohermal Trois-Fontaines Formation (Givetian). The Kačák event is identified in the transgressive system tract of this sequence. The geographic distribution of facies and of reefs in particular led to the recognition of at least six sedimentation areas corresponding most probably to synsedimentary faulted blocks here defined as the Eau Blanche, Viroin, Lesse, Ourthe, Condroz and Sambre blocks. These sedimentation areas structured the Namur-Dinant Basin and recorded distinct depositional history and were probably active during the Devonian and Carboniferous interval.

The Kačák event (late Eifelian, Middle Devonian) on the Belgian shelf and its effects on rugose coral palaeobiodiversity

“…The Eifelian strata are represented by the grey line. Modified from Ziegler (1982) and Denayer (2019).…”

“…A short description of the lithostratigraphy is provided here. For further details, refer to Bultynck et al (1991), Bultynck & Dejonghe (2001) and Denayer (2019).…”

“…Legend & abbreviations: 1 -Baileux; 2 -Couvin; 3 -Nismes; 4 -Wellin; 5 -Resteigne; 6 -Jemelle; 7 -Hampteau; MD -Middle Devonian sequence; LST -lowstand system tract; TST -transgressive system tract; HST -highstand system tract; TSA -Tienne Sainte-Anne Member. Modified from Denayer (2019). (May 1995).…”

“…(Bultynck & Dejonghe 2001). Denayer (2019) interpreted these silicoclastic deposits as the lowstand system tract of the Middle Devonian third-order sequence MD4. These deposits are well-developped in the eastern part of the Namur-Dinant Basin where the subsidence rate was apparently the highest (Godefroid 1968, Kasimi & Préat 1996.…”

“…were reported in other places in the basin, notably in the Couvin area (Barchy & Marion 1999) where it seems to fill palaeodepressions between the highs formed by the underlying Tienne Sainte-Anne Mb. (Denayer 2019).…”