Late Holocene palynology of a saline lake in the Pantanal of Nhecolândia, Brazil

Abstract

This work presents the first description of a palynological assemblage preserved in sediments deposited in a saline lake (salina) in the Nhecolândia area of the Brazilian Pantanal. Pollen studies from salinas have been underappreciated due to inferred taphonomic issues related to elevated alkalinity. We have found a well-preserved assemblage that allowed the reconstruction of the history of local vegetation. Radiocarbon dating revealed a constant deposition since ∼3760 calibrated years before present (cal yrs BP), and pollen analyses suggested two main phases of vegetation and environmental development. From 3760 to 1510 cal yrs BP, the site was a swamp to shallow lake dominated by cattails (Typha domingensis) and Poaceae. From 1510 cal yrs BP to the present the herbaceous community is enriched with Cyperaceae and Bromeliaceae, and with tree taxa such as the Arecaceae (palm trees), evidencing the local development of a fringe vegetation. These two phases were interpreted as a change from drier to wetter settings, largely in agreement with regional lake and speleothem records, as well as pollen and carbon isotope studies from other locations in central South America during the latest Holocene. Given that salinas are non-floodable and pollen was found to be well preserved, we highlight the potential of palaeopalynology in these environments as a source of palaeoecological information for the Pantanal Basin.