Late Quaternary palaeoenvironmental evolution and sea level oscillation ofSanta Catarina Island (southern Brazil)

Sea level oscillation during the Quaternary played amajor role in the geomorphology and vegetation dynamics of coastal areas insouthern Brazil, encompassing ecosystems that often have a uniquebiodiversity. Understanding the natural evolution of these areas isessential for decision making regarding land use regulations towards sustainabledevelopment, as well as to preserve the uniqueness of the coastal ecosystems.The southern Brazil coastal plain is formed by marine, transitional andcontinental Quaternary deposits controlled by past variations of the sealevel. These variations shaped the coastal landscape and influenced thedevelopment of different Atlantic rainforest formations, such as mangrovesand restingas. In particular, the restinga formation corresponds to aspecific ecosystem that covers sandy soils of marine and fluvial-marineorigin formed during the Quaternary on the Brazilian coastal plain. In thiscontribution, we present high-resolution palynological and stable isotopedata from a Holocene core retrieved from the coastal plain of SantaCatarina Island (southern Brazil). We were able to identify four differentenvironmental zones for the last 6520 yr BP. The first zone (6520-2920 cal yr BP) is characterized by a lagoon with large marine-water influence.Notably, the observed dinoflagellate cyst association suggests that marinewaters entering the region had their origin in the relatively warm and salineBrazil Current waters. During the second zone (2920-1520 cal yr BP), marine-water contribution to the lagoon decreased until it became disconnected fromthe sea. The third zone (1520-550 cal yr BP) was marked by the decrease ofthe water level until it dried out and led to the colonization of herbaceousvegetation over the palaeo-lagoon. The last zone (550 cal yr BP-recent) ischaracterized by the consolidation of the coastal-plain Atlantic rainforest(restinga vegetation). Our results form an example of the strong sensitivityof southern Brazilian ecosystem change caused by relative sea levelvariations. As such, this study might contribute to the debate about the potentialeffects of current climate change induced by global sea level variations.