Tracing sea-level changes during the mid-Holocene in the southern Mediterranean coast: An example from the Gulf of Gabes

Abstract

Mid-Holocene sea-level emergence was recorded along a mid-latitude coastal site in the Gulf of Gabes, Tunisia, in beach rock deposits. However, the post-emergence sea-level curve and associated hydro-sedimentary processes have rarely been documented. This study presents new records of sea-level changes along the Tunisian coast since the mid-Holocene. Each phase of the sea-level curve was evidenced and supported by lithostratigraphic, morphological and archaeologic markers. Post-emergence sea-level fall due to postglacial isostatic rebound was recognized in regressive sequences which vary depending on available accommodation space, from a small pocket beach to a well developed dune system. Sea-level stabilization following isostatic rebound has promoted the end phase deposits of the regressive sequences. However, this stability was interrupted during the late Holocene by a high-energy storm event that accumulated a transgressive boulder unit at 2 m above present. Shape and disposition of the boulder ridge behind a prograding modern shoreline suggests that sea level has not changed during the late Holocene. The existence of a Roman fish pond on the upper foreshore confirms stability of sea level during the last two millennia. The combination of lithostratigraphic, morphological and archaeologic markers represents a tool for improving the accuracy of dating of erosional and depositional periods in mid-coastal sections.