Cyrille Prestianni ¹, Kenneth Higgs², Maurice Streel ³

¹ Royal Belgian Institute of Natural Sciences, Paleontology Department, 29, Rue Vautier, B-1000, BRUXELLES, Belgium. cyrille.prestianni@gmail.com

² University College of Cork, Geology Department, School of Biological, Earth and Environmental Sciences, University College Cork, Ireland. k.higgs@ucc.ie

³University of Liège, Geology Department, Allée du Six Août, Bat. B18, Sart Tilman, B-4000 LIEGE 1, Belgium.  Maurice.Streel@ulg.ac.be

       The Diducites versabilis-Grandispora cornuta (VCo) Zone was defined by Streel et al. (1987) as an Oppel Zone i.e. a zone characterized by an association or aggregation of selected taxons of restricted and largely concurrent range chosen as indicative of approximate contemporaneity. Judgement may vary however as to how many and which of the selected diagnostic taxa need to be present to identify the zone (Hedberg 1976). The VCo Zone was defined by the first appearance of Grandispora cornuta and Rugospora radiata (then flexuosa). Retusotriletes phillipsii was added later as an additional zonal species, due to the importance given to this species in the Famennian of eastern North America (Clendening et al. 1980, Richardson & McGregor 1986). However, its range in the late Famennian of the Ourthe valley, where the zone was originally defined, has never been really established. A major problem has also arisen with regard to the use of Rugospora radiata as a zonal index species for the VCo Biozone, because of difficulties in discrimination between R.radiata and the morphologically similar late Frasnian-early Famennian taxon Rugospora bricei Loboziak & Streel (1989). These difficulties have resulted in the older stratigraphical extension of the VCo Zone range in some regions. Therefore, in this paper we propose to specify the VCo Oppel Zone with a new Grandispora  cornuta (Gc) Interval Zone, with the base being defined by the first appearance of Grandispora cornuta. The top of the Gc Zone is marked by the first appearance of Grandispora echinata (Higgs et al. 2000), a morphologically related taxon, one of the characteristics of the base of the overlying Apiculiretusispora verrucosa-Vallatisporites hystricosus (VH) Oppel Zone as defined by Maziane et al. (1999). A detailed morphological analysis of Grandispora cornuta and other related Grandispora species has been undertaken involving the study of both new material obtained from the Namur and Dinant basins in Belgium and old published material. This review has allowed the authors to separate more clearly than before Grandispora cornuta from the frequent and often abundant Grandispora tamarae. The age of the base of this new Grandispora cornuta (Gc) Interval Zone is correlated with the late postera or early expansa conodont zones. The correlations of the Gc interval Zone in W-Europe, E-America and W-Gondwanan regions are evaluated.

References

Clendening, J.A., Eames, L.E., Wood, G.D. (1980). Retusotriletes phillipsii n.sp., a potential Upper Devonian guide palynomorph. Palynology 4: 15-22.

Hedberg, H.D., Editor (1976). International Stratigraphic Guide. Wiley, N.Y., 200 p.

Higgs, K.T., Avkhimovitch, V.I., Loboziak, S., Maziane-Serraj, N., Stempien-Salek, M., Streel, M. (2000) Systematic study and stratigraphic correlation of the Grandispora complex in the Famennian of northwest and eastern Europe. Rev. Palaeobot. Palynol. 112: 207-228.

Loboziak, S.& Streel, M.(1989). Middle-Upper Devonian Miospores from the Ghadamid Basin (Tunisia-Lybia): systematics and stratigraphy. Rev. Palaeobot; Palynol., 58: 173-196.

Maziane,N., Higgs, K.T., Streel, M. (1999). Revision of the late Famennian miospore zonation scheme in eastern Belgium. Journal of Micropalaeontology, 18:17-25.

Richardson, J.B., McGregor, D.C. (1986). Silurian and Devonian spore zones of the Old Red Sanstone . Geol. Surv.Canada Bull. 364: 1-79.

Streel, M., Higgs, K.T., Loboziak, S., Riegel, W., Steemans, P. (1987). Spore stratigraphy and correlation with faunas and floras in the type marine Devonian of the Ardenne-Rhenish regions. Rev. Palaebot. Palynol. 50: 211-229.