Stratigraphy and depositional environments of the Late Famennian (Late Devonian) of Southern Belgium and characterization of the Strud locality

Abstract

The Famennian (Upper Devonian, c. 372 to 359 Ma) strata of Belgium have recently received much attention after the discoveries of early tetrapod remains and outstandingly preserved continental arthropods. The Strud locality has yielded a diverse flora and fauna including seed-plants, tetrapods, various placoderm, actinopterygian, acanthodian and sarcopterygian fishes, crustaceans (anostracans, notostracans, conchostracans and decapods) and a putative complete insect. This fossil assemblage is one of the oldest continental – probably fresh-water – ecosystems with a considerable vertebrate and invertebrate diversity. The study of the palaeoenvironment of the Strud locality is crucial because it records one of the earliest and most important phases of tetrapod evolution that took place after their emergence but before their terrestrialization. It raises the question of environmental and ecological conditions for the Devonian aquatic ecosystem and the selection pressures occurring at the onset of tetrapod terrestrialization. The present study characterized the fluvial facies of the Upper Famennian sedimentary rocks of Strud and the surrounding areas. The exceptional preservation of arthropods and plants in the main fossiliferous layers is explained by rapid burial in the fine-grained sediment of the quiet and confined flood plain environment. Newly investigated fossiliferous sections in the Meuse–Samson area led to the description and correlation of key sections (Strud, Wierde and Jausse sections, complemented by the less continuous Haltinne, Huy and Coutisse sections). Moreover, the investigated sections allowed a review of the age of the fossiliferous horizon, which is now definitely considered to be Late Famennian in age.

Characterization of the placoderm (Gnathostomata) assemblage from the tetrapod‐bearing locality of Strud (Belgium, upper Famennian)

“…The fossiliferous strata of this quarry (lithological unit UL7) belong to the Upper Devonian Evieux Formation (Denayer et al . in press; Fig. B, C).…”

“…The stratigraphical section at Strud belongs to the Haine–Sambre–Meuse Overturned Thrust Sheets (HSM OTS), which is a Variscan structural element of the Namur–Dinant Basin (Denayer et al . in press; Fig. A).…”

Update of the Devonian lithostratigraphic subdivision in the subsurface of the Campine Basin (northern Belgium)

“…Concerning the conodont zonation, it is remembered that the Palmatolepis rhenana and P. linguiformis Zones are present in the Upper Frasnian and succeeded by the P. triangularis and P. crepida Zones in the Lower Famennian (Coen-Aubert, 2016;Denayer et al, 2016). …”

“…The Evieux Formation, normally Upper Famennian in age, seems to be the only unit from the Condroz Sandstone Group present in the Campine Basin (Laenen, 2003;Thorez et al, 2006). According to Denayer et al (2016), a new unnamed formation should be introduced to regroup the classical Montfort and Evieux Formations defined in the Ourthe valley, to the south of Liège.…”

“…The Bois des Mouches Formation has been introduced by Delcambre & Pingot (2000) directly above the Falisolle Formation, on the map sheet Fontaine-l'Evêque -Charleroi. The Falisolle, Esneux and Bois des Mouches Formations have been used or discussed recently in the Namur Basin, by Denayer et al (2012Denayer et al ( , 2016 and Coen-Aubert (2015). (Coen-Aubert, 2014) Frechastraea limitata Potyphyllum ananas Thecostegites cf.…”