## 5 Results
Indeed, most of them are adjacent to springs, river channels and wetlands, and it is thought that the menhir status may have had a \"protective\" role in preventing water resources from silting up [98,99]. In the Lower Sagone Valley (SW Corsica), a large deltaic plain formed over the last three millennia [97], even if the present-day landscape configuration indicates no coastal wetlands (lagoons or ponds). Archaeological studies have identified numerous anthropomorphic menhir status on the west bank of the Sagone River [102], some of which were reused in medieval structures (Figure 4a-c) or otherwise removed from their original location (Figure 4d). Paleoenvironmental research conducted in the mid-2010s [97] was based on coring evidence. A mechanism of rapid deltaic progradation starting ca. 800 cal. BCE was revealed and was probably partly caused by the 2.8 ka BP ongoing climatic deterioration, which provoked the initial large-scale phase of deltaic progradation of large rivers situated on the north Tyrrhenian coast [103,104,105]. Surprisingly, the coring results also indicate the existence of a freshwater environment on the west bank of the present-day river bed where the menhir status were discovered (Figure 5). The base of this freshwater environment has not yet been reached (it dates at least from the beginning of the Middle Bronze Age, ca. 1700 cal. BCE), but a clear transition from a coastal freshwater wetland to a marine environment has been dated at ca. 1100 cal. BCE (Figure 5 [97]). The complete palaeogeographic reconstruction of the Sagone deltaic plain first aimed to better understand the landscape evolution and then to precisely evaluate changing environmental conditions from the beginning of the Middle Bronze Age (MBA) until modern times (Figure 5), with a specific focus on the supposed period of appearance of the menhir status during the Late (LBA) or Final Bronze Age (FBA). Figure 4: Archaeological evidence for the occupation of the Lower Sagone Valley. Sant\({}^{\prime}\)Appianu Cathedral view (**a**) with reuse of menhir status as foundation stones (**b**,**c**); [PERSON] (**d**). These results make it clear that a freshwater environment prevailed before marine ingression dated ca. 1100-1000 cal. BCE. It is noteworthy that several short episodes of marine incursion had already occurred ca. 1200-1100 cal. BCE (FBA), resulting in the deposition of marine-sandy layers in the rich organic clays of the swamp (Figure 6). In terms of land use, pollen results reveal that the LBA (1350-1200 cal. BCE) contrasts with the MBA in the sharp decline of both cereal cultivation and pastoralism (Figure 6) around 1350 cal. BCE. Pollen and NPP data (Figure 6) clearly suggest a phase of less human occupation at the end of the Middle Bronze Age and spanning the entire Late Bronze Age. However, the freshwater-coastal pond existed during both periods and thus cannot be used as an environmental argument to explain a sudden change in social organization. The case study presented here for the Lower Sagone Valley landscape evolution demonstrates the necessity to investigate archaeological questions by adopting a geoarchaeological approach. On this point, it is important to note that continuity of the human occupation is attested at the same location from the Recent Bronze Age until the medieval times and thus obviously indicate that the environmental (topography and specific landscape) configuration played a major role in the installation of sites. Figure 5: Palaeogeographic reconstruction of the Sagone Plain from the Bronze Age to Late Modern times. The interpretation is based on the combination of sedimentological data and ERT measurements obtained for the present study, together with the 1970s boreholes drilled for geotechnical purposes. Reconstructing Vegetation History, and the Importance of Studying Anthropogenic Markers to Enlarge Knowledge of Human Occupation and Land Use  
Coastal areas of Corsica have recently been investigated to reconstruct their vegetation history with a specific focus on anthropogenic markers [73].