Planktonic foraminiferal evidence of Late Cretaceous movements in the Gulf of Hammamet area (northeastern offshore Tunisia)

Abstract

The gulf of Hammamet (GH) area, located in northeastern offshore Tunisia, experienced several tectonic deformations during the Mesozoic and Cenozoic eras. These deformations generated discontinuities, hiatuses, and thickness variations of sedimentary successions during the late Cretaceous, such as the late Campanian-late Thanetian El Haria Fm, which is documented to be partially or totally eroded in the GH area. Several geological works based on geophysic, seismic, and log data in the GH area attribute the existent (thinner) part of the El Haria Fm to the Palaeocene. The present study analyzes the planktonic foraminiferal biostratigraphy of this thinner part of the El Haria Fm in the well A-1 located in the northeastern part of the GH area. The analyzed foraminiferal assemblages highlight the existence of a Danian sequence (6.1 m) unconformably deposited above a Maastrichtian sequence (12.2 m), which rest unconformably on a late Campanian sequence (12.2 m). The foraminiferal record also indicates the occurrence of three hiatuses across the Campanian-Maastrichtian, early-late Maastrichtian, and Maastrichtian-Danian boundaries, respectively. The correlative data and timelines from the surrounding wells helped to decipher the morphology of the substrate underlying the El Haria Fm (i.e., the Abiod Fm) in the GH area and the distribution pattern of the deposited Campanian-Thanetian sequences. This work depicts subsiding areas towards the northeastern and southwestern parts of the GH area. These subsiding areas are correlative with swells in the southeastern part of the study area, which grade to a NW-trending bald zone without record of the Abiod and El Haria formations.