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Integration of new data in sedimentology, micropalaeontology and organic carbon isotopeanalysis of upper Ypresian strata in central Belgium (Zemst hole) enables differentiationof a series of biotic events and carbon isotope trends, which are believed to be associated with the 1.5-million-year-long period of global warming, known as the Early Eocene Climatic Optimum (EECO). The relatively low values in δ13Corg(-26.5‰ to -27.1‰) in the interval from the Panisel Sand to the Merelbeke Clay Members (upper NP12-lower NP13) are shown to be coinciding with a fairly high frequency in Apectodinium (>3%, up to 14%) and a Discoaster-bloom (16%-50%, essentially D. kuepperi). This is quite analogous, although less prominent, to what has been observed during the Paleocene-Eocene Thermal Maximum (PETM: Apectodinium abundance of 75% at middle and high latitudes and Discoaster blooms in tropical areas). The abrupt positive shift of up to 1‰ in δ13Corg values at the base of the overlying Pittem Clay Member (mid-NP13, mid-chron C22r), which is coincident with the virtual disappearances of Apectodinium (Discoaster (Blackites inflatus), as adopted in the Gorrondatxe GSSP (Spain), cannot be applied in the North Sea Basin s.s. (excluding the Paris Basin) and that there is an urgent need for defining appropriate substitutes for this boundary at these latitudes.

Utilizing bio- and chemostratigraphy, we propose an integrated dating of the upper part of the continental “Sparnacien des Corbières” and the overlying marine “lower-middle Ilerdian” succession of AlbasLe Clot (Corbières, France), in order to refine the position and age of the Le Clot mammalian locality. Our data show that this locality, which has yielded a mammal fauna early Ypresian in age (close to MP7, Mammal Paleo gene level), is located above the end of the carbon isotope excursion (CIE) the base of which defines the Paleocene–Eocene boundary. The Le Clot mammalian locality is therefore younger than the Paleocene–Eocene Thermal Maximum (PETM), and also younger than the Dormaal MP7 reference fauna in Belgium, which is correlated with the onset of the CIE (nannoplankton Zone NP9b). Moreover, we demonstrate that the Le Clot mammalian locality is older than the Eocene Thermal Maximum 2 (ETM2) event, located in the lower part of NP11 Zone. Associated with the ages of benthic foraminifera and dinocysts observed in the succession, our d13Corg chemostratigraphy suggests that the Le Clot locality is correlated to the upper NP10–lower NP11 Zones. The refined location of the CIE in the Albas-Le Clot section is discussed because two carbon isotope excursions are potentially recorded in the upper “Sparnacien des Corbières”, here recognized as mainly Thanetian in age.

Despite the large number of studies on the Paleocene–Eocene thermal maximum (PETM), the knowledge of environmental and biotic responses in shallow marine environments remains quite poor. Benthic foraminiferal assemblages of the Sidi Nasseur and Wadi Mezaz sections in Tunisia were studied quantitatively and the paleoecologic interpretations provide new insights into the complex relationship between PETM global warming and perturbations of shallow marine settings. These sections expose upper Paleocene to lower Eocene shales and marls of the El Haria Formation up to the phosphate layers of the Chouabine Formation underlying the El Garia limestones. The Sidi Nasseur section contains a more complete and expanded Paleocene–Eocene boundary interval compared to Wadi Mezaz, although being truncated at the top. The Wadi Mezaz section contains a more complete post-PETM interval. The studied interval can be subdivided into a sequence of 4 biofacies, representing respectively a latest Paleocene biofacies, two PETM biofacies and one post-PETM Eocene biofacies.The latest Paleocene biofacies 1 consists of numerous calcareous benthic foraminifera (e.g. Anomalinoides midwayensis, Frondicularia aff. phosphatica and various Bulimina and Lenticulina species), abundant non-calcareous taxa (Haplophragmoides) and rare planktic foraminifera, indicating a slightly hypersaline eutrophic inner neritic to coastal environment, regularly interrupted by oxygen deficiency (moderate dysoxia). During the latest Paleocene, this highly productive environment shallowed as indicated by the increasing abundances of A. midwayensis. The variable dominance of non-calcareous agglutinated taxa in biofacies 1 indicates post-mortem dissolution effects. The TOC d13Corg record reveals a sharp negative excursion, marking the base of the Eocene. In general, the absence of lithologic changes, an increasing sedimentation rate and absence of reworking indicate that the initial part of the PETM is complete and expanded in the Sidi Nasseur section. A sharp faunal turnover coincides with this negative d13Corg excursion and is characterized by the disappearance or diminution of common Paleocene taxa in this area. During the PETM, benthic foraminifera are less abundant and consist of opportunistic non-calcareous taxa together with deeper dwelling (middle neritic) lagenids and buliminids (biofacies 2 and 3). Planktic foraminifera, dominated by flat-spired Acarinina (mainly A. multicamerata), become more abundant, as observed in many open marine sequences worldwide. All these faunal parameters suggest more stressed probably severe dysoxic sea floor conditions within a transgressive phase during the onset of the PETM. An estimation of the total duration of the Sidi Nasseur PETM interval is difficult to establish, yet the lack of recovery carbon isotope values suggests that the preserved PETM interval reflects only a part of the CIE “core”. The top of the PETM interval is truncated due to local (?) erosion during the early Eocene. The Eocene recovery fauna is mainly composed of Lenticulina and Stainforthia species (biofacies 4), indicating restricted coastal to hyposaline lagoonal eutrophic conditions, distinctly different from earlier environmental conditions.

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