Spatial evolution and archaeological contextualization through Holocene Edapho-sedimentary deposits: Areoso Island (NW Spain)

Areoso Island is located in the inner part of the Ría de Arousa, located on the Atlantic coast of northwestern Spain. With an area of 8 ha, it has a high density of Neolithic burial mounds. The island has a varied geomorphological heritage, highlighting the granite geoforms or the presence of edapho-sedimentary deposits. These coastal deposits are quaternary formations made up of unconsolidated material, which appear discontinuously throughout the Galician coastline. The analysis of its facies allows to detect past environmental changes, the study of which is of great interest in the field of Earth Sciences and of great use for other disciplines such as Archeology. the island has a high archaeological interest, highlighting the documented presence of five Neolithic funerary tumuli. At present, these constructions are threatened by marine erosion, derived from unique morphodynamic conditions. The deposits were sampled in different sectors and environments of the island, obtaining an almost continuous chronological sequence of the edapho-sedimentary formation during the last 6000 years. This allowed reconstructing the palaeoenvironmental evolution, differentiating several stages, where the Holocene transgression played a fundamental role in its formation. 6000 years ago, with a sea level lower than today, the emerged surface was much higher than in the present, and could even be connected to the continent. These facts are relevant to archaeological interpretation, as they suggest that the burial mounds were not built in a coastal setting. The study of the ancient deposits of Areoso allows obtaining different proxies (sedimentary, geochemical, biological, archaeological), which are of great help to interpret the archaeological context, since anthropic activities are reflected in the resulting deposits. The high scientific and didactic interest of the ancient edapho-sedimentary formations makes it necessary to put them in value. This palaeoenvironmental information means that they should be considered natural heritage. In the current context of rising sea levels, many of them are seriously threatened, so it is necessary to promote their management and geoconservation, to the extent that natural processes allow. The objective of this work is to value them and proclaim their importance as environmental records.