Palynostratigraphy of the Tournaisian (Hastarian) rocks in the Namur Synclinorium, West Flanders, Belgium

Abstract

The first detailed palynostratigraphy of the Hastarian in Belgium is described. The Hastarian is the lower subdivision of the Belgian Tournaisian and spans the Tn1b and Tn2 lithostratigraphical units. A succession of well to moderately well preserved miospore assemblages has been obtained from this stratigraphical interval in five boreholes located in the western part of the Namur Synclinorium, where the Hastarian succession is represented by a mixed sequence of marine clastic and carbonate rocks. These miospore assemblages are assigned to four biozones (VI, HD, BP, and PC) of the miospore zonation scheme established for the Tournaisian rocks of southern Ireland. Detailed sampling in the lower part of the Hastarian succession in the Namur boreholes has allowed a finer resolution of the Kraeselisporites hibernicus—Umbonatisporites distintus (HD) Miospore Biozone, based on the successive first appearances of the two zonal species. Correlation of the miospore biozones with conodont faunas obtained from the same boreholes indicates that the HD Miospore Biozone equates with the Siphonodella sandbergi and lower S. crenulata Conodont Zones, the BP Miospore Biozone spans the boundary between the lower and upper S. crenulata Conodont Zones, and the base of the PC Miospore Biozone occurs within the upper S. crenulata Conodont Zone.