Unraveling the Paleocene-Eocene thermal maximum in shallow marine Tethyan environments: the Tunisian stratigraphic record

Abstract

Despite the increasing understanding of the Paleocene-Eocene thermal maximum (PETM) in open marine environments, shallow marine settings remain relatively unexplored. We investigated an upper Paleocene to lower Eocene shallow-water sequence near Kalaat Senan in Tunisia (Sidi Nasseur and Wadi Mezaz sections) in order to generate a stratigraphic framework of the PETM in a shallow marine fine-grained siliciclastic setting of the Southern Tethys. These sections expose the top part of the El Haria Formation (Fm.), the Chouabine Fm. and the lower part of the limestone bearing El Garia Fm., covering the upper Paleocene- lower Eocene (NP9a to NP11). The PETM interval is situated near the top of the El Haria Fm. and the re- gional stratigraphy is compared to the well-known Egyptian setting. The isotope record of total organic car- bon (δ 13 Corg) reveals the characteristic negative carbon isotope excursion (CIE), comparable to the δ 13 Corg record of the Global Boundary Stratotype Section and Point of the Eocene at Dababiya (Egypt). Although the Tunisian PETM interval is quite expanded, no anomalous beds are observed and only the CIE core is part- ly represented as the top part of the PETM is truncated. In addition to a well-expressed CIE, the position of the Paleocene-Eocene boundary is supported by the appearance of nannoplankton (Discoaster araneus) and foraminiferal (e. g. Acarinina multicamerata) marker taxa. Furthermore, ostracode and benthic foraminifer- al turnovers coincide with the onset of the PETM and are characterized by the disappearance of many com- mon Paleocene taxa (e. g. Frondicularia aff. phosphatica) in this area. The lowest occurrences of Alo- copocythere attitogonensis and Buntonia? tunisiensis (ostracodes), Reophax sp. 1 (benthic foraminifera) and Fasciculithus tonii (calcareous nannoplankton) may be applicable for regional correlation. These results in- dicate that characteristic PETM taxa evolved and/or dispersed immediately after the main δ 13 Corg shift.