Salt marsh palynological assemblages as modern analogue tools for interpreting past vegetation zones and environmental conditions in the NE coastal plain of Argentina

Abstract

In this study we examine the distribution patterns of modern palynological assemblages from different salt marsh zones and microenvironments in order to generate reference data for the north-central sector of Bahía Samborombón, to be used as analogues for interpreting fossil palynological assemblages. For the modern palynological analysis, 23 surface sediment samples were taken from different tidal environments in the coastal zone, including intertidal, low, middle and high salt marsh. The results allowed to differentiate and characterize the tidal environments from the palynological point of view. Small changes in the microrelief such as tidal channels, cheniers, and depressions areas, modify the local vegetation and therefore determine the final palynological assemblage. Fossil data from the central zone of Bahía Samborombón (PM 1 stratigraphic sequence) was compared with the modern pollen data to interpret vegetation and paleoenvironmental changes; which demonstrated that salinity, mainly related to the tidal influence, drove the paleoenvironmental changes. This study provides new modern palynological data for Bahía Samboromb´on and may constitute an important tool to interpret Holocene fossil sediment sequences. This data could be used in future paleoenvironmental reconstructions in coastal plain deposits whose evolution are linked to relative sea-level fluctuations.