Updating Frasnian miospore zonation from the Boulonnais (Northern France) and comparison with new data from the Upper Palaeozoic cover on the Brabant Massif (Western Belgium)

Abstract

Accurate palyno-analysis by S. Loboziak (from 1980 to 1983) of 28 samples from the Upper Givetian to the Middle Frasnian Blacourt, Beaulieu and Ferques Formations and of 44 samples of the Upper Frasnian to the Lower Famennian Hydrequent Formation are re-evaluated. Chelinospora concinna, Verrucosisporites bulliferus, Cirratriradites jekhowskyi, Lophozonotriletes media first occurrences are major criteria for Lower and Middle Frasnian, well calibrated by conodonts. Cymbosporites acanthaceus, Rugospora bricei, Grandispora gracilis, Diducites plicabilis, Corbulispora vimineus first occurrences allow to subdivide the Upper Frasnian where conodonts are poorly present. Samarisporites triangulatus versus Auroraspora pseudocrista taxonomy and stratigraphic significance are discussed. The reconnaissance borehole Nieuwkerke-De Seule (95W152), near the limit of the Upper Palaeozoic subcrop on the Brabant Massif (West Flanders, Belgium, 75 km east of the Boulonnais), which has intersected conodont-dated Givetian/Frasnian boundary at the transition between the Bois de Bordeaux and Bovesse Formations, contained poorly preserved miospores attributed to the triangulatus–concinna (TCo) Oppel Zones. In the nearby Nieuwkerke-Noordhoek borehole (95W153), strata also assigned to the Bovesse Formation yielded better preserved miospores which demonstrate a close succession of triangulatus–concinna (TCo) and bulliferus–jekhowskyi (BJ) Oppel Zones at the transition Lower–Middle Frasnian, also known in the Beaulieu Formation in the Boulonnais. Samples from the Heuvelland groundwater monitoring well (95W175), 10 km north of Nieuwkerke, contain the bricei-acanthaceus (BA) Oppel Zone suggesting a late Frasnian age, also known in the Hydrequent Formation in the Boulonnais area and in the Booischot Formation in the Booischot borehole (59E146) from the Campine Basin (Belgium). International correlation using Frasnian miospore zonation is attempted between the Pripyat Depression in Belarus, the Timan–Pechora province in Russia and North-West China.