Flooding a landscape: impact of Holocene transgression on coastal sedimentology and underwater archaeology in Kiladha Bay (Greece)

Abstract

Franchthi Cave, bordering Kiladha Bay, in Greece, is a key archaeological site, due to its long occupation time, from * 40,000 to * 5000 year BP. To date, no clear evidence of Neolithic human dwellings in the cave was found, supporting the assumption that Neolithic people may have built a village where there is now Kiladha Bay. During the Neolithic period/Early Holocene, wide areas of the bay were indeed emerged above sea level. Bathymetric and seismic data identified a terrace incised by a valley in * 1 to 2 m sediment depth. Eight sediment cores, up to 6.3-m-long, were retrieved and analysed using petrophysical, sedimentological, geochemical, and chronostratigraphic methods. The longest core extends into the exposure surface, consisting of a layer of carbonate rubble in a finer matrix, representing weathering processes. Dated organic remains place this unit at * 8500 cal year BP. It is overlain by stiff silty mud representing an estuarine environment. This mud is capped by reduced sediments with roots marking an exposure surface. A shell-layer, dated to * 6300 cal year BP, overlies this terrestrial sequence, reflecting the marine transgression. This layer occurs at 10.8 mbsl, 7.7 m deeper than the global sea level at that time, suggesting tectonic subsidence in the area. It is overlain by finer-grained marine carbonate-rich sediments. The top of the core shows traces of eutrophication, pebbles and marine shells, all likely a result of modern anthropogenic processes. These results are interpreted in the context of human occupation: the exposed surface contains pottery sherds, one dating to the Early to Middle Neolithic period, indicating that Neolithic people were present in this dynamic landscape interacting with a migrating coastline. Even if the artefacts are isolated, future investigations of the submerged landscape off Franchthi Cave might lead to the discovery of a Neolithic village, which eventually became buried under marine sediments.

The impact of environmental change on Palaeolithic and Mesolithic plant use and the transition to agriculture at Franchthi Cave, Greece

“…The non-wood botanical evidence indicates very limited plant-food use during this period, which is distinguished by an emphasis on tuna fishing [ 14 , 18 ]. It is possible that, apart from the increasing inundation of the coastal shelf by SLR, the increasing salinization of the Franchthi River due to rising sea-levels had also began affecting the availability of wild cereal and legume stands on the FC terrace and the riverine floodplain alluvium that formed a dominant feature of the local landscape during the early Holocene [ 34 – 35 ].…”

8,000 years of climate, vegetation, fire and land-use dynamics in the thermo-mediterranean vegetation belt of northern Sardinia (Italy)

“…The Mediterranean Sea rose 15 m between 9,000 and 8,000 cal bp, while in the following 8,000 years the further increase was only ca. 5 m to reach modern conditions (Brisset et al 2018;Surdez et al 2018;Vacchi et al 2018). We assume that the Early Holocene transgression caused the formation of lagoons in Sardinia, with the sea-level rise promoting the rise of groundwater tables as well as the retention of freshwater in the retro-dunal depressions (Surdez et al 2018).…”

“…5 m to reach modern conditions (Brisset et al 2018;Surdez et al 2018;Vacchi et al 2018). We assume that the Early Holocene transgression caused the formation of lagoons in Sardinia, with the sea-level rise promoting the rise of groundwater tables as well as the retention of freshwater in the retro-dunal depressions (Surdez et al 2018). Today water salinity is moderate at Lago di Baratz, with Na reaching concentrations of 350-400 mg/L and Cl 620-660 mg/L, allowing freshwater animals and plants to thrive (Mongelli et al 2013).…”

Archaeological prospection in ultra‐shallow aquatic environments: the case of the prehistoric submerged site of Lambayanna, Greece

“…The wider area has been identified as a horst block bordered by two reverse faults (van Andel, 1987). A systematic marine geological and geophysical survey employing sub‐bottom profiler and dual‐frequency side scan sonar indicated palaeo‐shorelines, morphological terraces, palaeo‐sea level indicators and palaeo‐ground surfaces (Surdez et al ., 2018).…”