Contribution of the palynology to the knowledge of embalsados in the Holocene of Corrientes, Argentina

Floating or embalsados islands in warm water bodies have few studies and share some structural properties with temperate-cold weather peat bogs for which there is more information. In Argentina, the references are reduced to the middle and lower courses of the Parana River, where the embalsados have a low frequency. The palynological analyzes carried out in the San Cristobal, Cue and Miranda lakes aim to increase knowledge about the development of this biome in the Holocene of northeastern Ibera, central region of Corrientes Province. Three cores of the bottom of the lakes were obtained and the ages were estimated by applying the age-depth model calibrated with radiocarbon dates. The qualitative-quantitative analysis of 38 palynological associations allowed the distinction of two intervals. Between 4300 and 3600 years cal BP, the vegetation was dominated by herbaceous species of angiosperms and chlorophycean algae representatives of aquatic environments, marshes and reed beds and to a lesser extent by dammed-forming species. From 3500 years cal BP onwards, the frequency and variety of aquatic species of angiosperms and chlorophycean algae decreases and the predominance of grassland species and colonizers of water mirrors increases. This change suggests the development of embalsados with the formation of organic soils in the Late Holocene, probably as a result of a greater clogging of lakes and reduction of water mirror with oxygen deficit and water acidity.