Socio-ecological adaptation to Early-Holocene sea-level rise in the western Mediterranean

Abstract

Consecutively to the global sea-level rise, coastal landscapes significantly changed during the Early Holocene. We explored how coastal mutations have affected ancient human systems in the western Mediterranean. The Pego-Oliva basin (Spain) provides a thick sediment sequence located in proximity to two well-studied Mesolithic and Neolithic archaeological sites. Based on 16 sediment cores, sedimentological analyses, 14 C dates, and integration of previous works, we reconstructed the architecture of the sedimentary facies and the chronology of deposition for the last 9500 years. From 9500 to 8200 cal. BP, the stepwise inland migration of the coastline is characterised by the deposition of peat layers at distinct depths indicating four phases of barrier-lagoon systems development. The marine transgression caused the disappearance of the lagoon at 8200 cal. BP, and reached a maximum inland position at 7300 cal. BP. Since 5800 cal. BP, sea-level stabilisation induced coastal progradation and barrier-lagoon system construction. Five marine flooding phases dated at 9500, 9100-9000, 8750-8650, 8450-8200, and 8100-7300 cal. BP match Atlantic meltwater pulses. Comparison to archaeology shows that the long-lasting Mesolithic occupation corresponds to the presence of coastal offering easily exploitable local intertidal resources. In contrast, during the Late Mesolithic, we observe a lagoon contraction and the reduction of lagoon bivalves size arguing for a decrease in resource productivity. This changes in the lagoon ecosystems negatively impacted to Late Mesolithic populations leading to a less intense occupation of this area. Therefore, the 700 years' temporal hiatus between the last hunter-gatherers and the first farmers occupying this area is explained by the disappearance of the formerly exploited biotopes because of sea-level rise, a situation that may have been aggravated by coincidence of the 8200 cal. BP climate event. The maximal sea transgression corresponded to a shift from intertidal to infralittoral species between the Impressa/Precardial and the Postcardial Neolithic, indicating a good adaptation to changing environments at that time. However, comparison between Late Mesolithic to Early Neolithic suggests that communities with different cultural baggage have had a different perception of the same environment. By the past perspective, it emphasises that perception of the ecosystem value as a benefit or constraint, and of the risks associated with sea-level rise, relies first on the local and regional scales adaptive capacity of society to global changes.

Mid‐ to late Holocene environmental changes and human‐environment interactions in the surroundings of La Silla del Papa, SW Spain

“…Indeed, the maximum transgression in the Zahara Bay must have occurred after 8300 BP (6400 BC, Z5/26), when a shell‐debris layer was deposited at Z5, and before 7000 BP (5000 BC, Z4/12), when salt marsh environments developed at Z4. According to Brisset et al (2018), this is comparable with the timing of the maximum transgression (~7200 BP) in the western Mediterranean. By then, the coastal zone experienced a metamorphosis from a primary coast (ria‐type coast) to a secondary coast (lagoon‐barrier coast).…”

Driving mechanisms of Holocene coastal evolution in the Bonifacio Strait (Western Mediterranean)

“…4). In this timespan, none of the models can reconcile the RSL evolution as already noticed in other portions of the western Mediterranean Sea (Brisset et al, 2018;. We speculate that this might depend on the ice-sheets models (shapes and sizes) as well as on the solid Earth parameters and stratification.…”

“…The results of the palaeoenvironmental reconstructions (see results section) revealed depositional facies associations typical for coastal lagoons, brackish swamps, and shallow-marine environments. All these facies can provide very useful insights into the sea-level evolution, notably in the Mediterranean context (e.g., Fontana et al, 2017;Brisset et al, 2018). Among them, lagoons and brackish swamps were widely used to produce relative Sea-Level Index Points (SLIP i.e.…”

“…Journal Pre-proof palaeo RSL in time and space; e.g. in Mediterranean sea-level studies (e.g., Fontana et al, 2017;Chelli et al, 2017;Brisset et al, 2018).…”

Environmental Changes and Cultural Transitions in SW Iberia during the Early-Mid Holocene

“…A reduction in the size of the shellfish collected was also identified in the transition from Mesolithic to Neolithic at Vale Boi, Rocha das Gaivotas, and Armação Nova, and it was considered a consequence of overexploitation [12] or a decrease in the foraging efficiency [121]. However, in some Mediterranean areas such as the Pego palaeolagoon, a reduction of lagoon bivalve size during the Late Mesolithic has been observed, related to a decrease in resource productivity [122]. Despite this there was gently increase in ocean organic productivity linked to the slow overall cooling of the waters during the Mid Holocene, the warmer climate during the Holocene Thermal Maximum caused a weakening of the coastal upwelling, briefly interrupted during the short cooling episodes [79].…”