Ostracods and sedimentology of the La Serre Devonian/Carboniferous stratotype section (La Serre, Montagne Noire, France)

摘要: Despite their low abundance, ostracods are very diversified in the La Serre Devonian-Carboniferous (= D-C) Global Stratotype Section and Point GSSP). Seventy-one species identified, 58 Devonian 29 Carboniferous. The ostracod fauna is composed of belonging to Eifelian ecotype alone or a mixed assemblage Thuringian ecotypes. relative abundance these two ecotypes, abnormal number instars some beds, presence oolites occurrence reworked specimens elements microbreccia give evidence for important changes conditions environment close D-C boundary. In Late Devonian, display regressive trend from deep environments below storm wave base highly agitated above fair-weather base. But sea level curve not completely recorded section since tectonic disturbed beds present upper part profile. disappearing during Hangenberg Event at seems be less comparison with other sections investigated Germany Poland. sedimentological study displays standard sequence six carbonate microfacies (MF1 MF6) shows quite abrupt transition shallow hemipelagic (MF1) shoreface-foreshore microbioclastic ooidal shoals (MF2-MF5) reaching beach foreshore (MF6). No subaerial emergence found, nor any sedimentary structures indicating intertidal restricted environments. Microbreccias abundant MF5 MF6; they moderately poorly sorted, subangular subrounded, show mixing different eroded microfacies. All this supports strong brief erosional phases within transitonal zone around 10 m water depth. points general regression starting near Horizon sensu FEIST et al. (2000), our sample 37 (Fig. 2), top (sample 64) as showed by shift 1 6 appearance proximal coquina layers, interpreted tempestites, toward section. energy was high indicated broken oolites, microbreccias lamination patterns. Finally increase (transgression) have occurred uppermost Sea-level fluctuations were probably about ten meters more, erosion whose fragments form 6. sedimentology confirm that far being an ideal GSSP.