Impact of latest-glacial to Holocene sea-level oscillations on central Aegean shelf ecosystems. A benthic foraminiferal palaeoenvironmental assessment of South Evoikos Gulf, Greece

A high-resolution palaeoenvironmental investigation was conducted on the benthic foraminiferal record of two continuous sediment cores (DEH 5, DEH 1) in order to reconstruct the latest-Pleistocene to Holocene history of the South Evoikos Gulf (central Aegean Sea). This shallow (max. depth ~75 m), semi-enclosed continental shelf setting has been heavily affected by the latest-glacial to modern-interglacial relative sea-level and climate oscillations that strongly affected the benthic foraminiferal community. The identified meiofaunal biofacies associated with the chronological framework allowed the recognition of four main time phases in the palaeoenvironmental and palaeobathymetric evolution of the gulf: (i) During the latest glacial-interglacial transition (> 15.17 ka BP), highly-stressed confined shallow lagoonal conditions correspond to the Last Glacial Maximum (LGM) sea-level lowstand. During that time, a natural barrier located at the mouth of the gulf effectively prevented communication with the open Aegean Sea and amplified the contribution of the local aquifers. (ii) The early post-LGM sea-level rise was initially marked by a weak marine connection, dominated by a pronounced seaward river progradation of local aquifers. However, immediately after (~14.7 ka BP), an enhanced rate of sea-level rise, synchronous with the Meltwater Pulse 1A (MWP-1A), is observed. At the end of the Pleistocene, the sedimentation rates decreased dramatically, as a result of the Younger Dryas (YD) cooling event. (iii) The Holocene sea-level rise was characterized by an extremely abrupt marine transgression (~11.29 ka BP), during which the sea-level in the Aegean Sea reached 55m below present sea level (b.p.s.l) and forcedly overcame the barrier that previously separated the gulf from the open sea. At ~8.67–7.77 ka BP, an upper circalittoral eutrophic environment emerged, which coincided with the coeval deposition of the sapropel S1 in the Eastern Mediterranean Sea. Immediately after, re-ventilation conditions were reinstated. (iv) The Holocene sea-level highstand is characterized by upper circalittoral high-energy and vegetated conditions on the sea floor. Regional index terms: Eastern Mediterranean; Central Aegean Sea; Greece; South Evoikos Gulf.