Terrestrial and marine palynomorph records as tools for reconstruction of the palaeoenvironment of the coastal plain of Paraty, Brazil, during the Holocene

Abstract Holocene environmental changes on the Paraty coastal plain in southeastern Brazil unfolded under dynamic sea-level fluctuations and shifting sedimentary regimes. Continental and marine palynomorph analyses, combined with calibrated radiocarbon dating from two sediment cores (JBS1 and JBS2), reveal a continuous depositional record spanning approximately 7800 to 1000 cal yr BP. Sandy mud and muddy sand sequences reflect variable coastal energy conditions through out the mid to late Holocene. Dinoflagellate cyst assemblages indicate a transition from open marine to marginal marine environments, with maximum marine influence between 7000 and 5000 cal yr BP. Terrestrial palynomorphs show a concurrent shift from grassland-dominated landscapes to mixed vegetation including ombrophilous forest taxa. A marked increase in pollen concentration in the upper stratigraphic layer suggests coastal progradation, enhanced continental input, and reduced marine influence during the late Holocene regression. Bayesian age-depth models demonstrate uninterrupted but variable sedimentation rates, with no evidence for erosional surfaces or depositional hiatuses. The results align with regional sea-level reconstructions and under score the role of transgressive-regressive processes and delta infilling in shaping vegetation dynamics. This integrated micropalaeontological and chronostratigraphic approach offers a robust framework for interpreting Holocene palaeoenvironmental evolution in tropical coastal settings.