Abstract
AbstractThe Upper Cretaceous boundaries have been analyzed globally by involving several taxonomic groups (e.g., ammonites, inoceramids, belemnites, foraminifers, nanofossils) in accordance with the recommendations of the Second International Symposium on Cretaceous Stage Boundaries in Brussels in 1995. However, a few chronostratigraphic boundaries are still under debate and need further clarifications (e.g., the Campanian–Maastrichtian (C-M) boundary). In this study, we focus on the Maastrichtian boundaries, based on planktic foraminifers from subsurface successions of central-eastern Tunisia. Three boundaries are highlighted: (1) a subsurface substitute for the newly defined C-M boundary, (2) a subsurface substitute for the early-late Maastrichtian boundary, and (3) the Cretaceous-Paleogene (K-Pg) transition. The C-M boundary is indicated by the last occurrence (LO) of Radotruncana subspinosa, which is correlated with the first occurrences (FOs) of the planktic foraminifers Rugoglobigerina scotti and Contusotruncana contusa, and the FO of benthic foraminifer Bolivinoides draco. The LO of Contusotruncana fornicata characterizes the early-late Maastrichtian boundary, which coincides with the FO of Abathomphalus mayaroensis. The first downhole occurrence (FDO) of most Upper Cretaceous planktic foraminifers indicates the transition from the Cretaceous to the Paleogene. The identified boundaries are correlated with two sections from north-western Tunisia in order to delineate their lateral extent and to evaluate their chronostratigraphic value. The present study also aims at a better understanding of the biostratigraphical record of the Maastrichtian successions in the Sahel domain and at highlighting undetectable lithostratigraphic units by using either seismic and/or log data.KeywordsCampanian–Maastrichtian boundary Radotruncana subspinosa Early-late Maastrichtian boundary Contusotruncana fornicata Central-eastern Tunisia
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