Holocene vegetation changes according to sea-level and climate dynamics on tidal flats of the Formoso River estuary, northeastern Brazil

Abstract

The aim of this work was to carry out a paleoenvironmental study of Holocene sedimentary deposits in the southern sector of Pernambuco's coast (northeastern Brazil). This work addresses an important aspect of Quaternary research that has implications for current climate debates, for instance, how does vegetation react to changing climate and rising sea levels. Thus, we provide a combined approach using sedimentological, palynological, geochemical analyses (stable isotopes i.e., δ13C, δ15N and C:N), in addition to AMS 14C dating from two surficial sediment cores i.e. T4 (up to 150 cm depth) and T5 (up to 136 cm depth) collected from the Formoso River estuarine system. Climatic oscillations show variation in precipitation and atmosphere humidity, marked by areas of expansion and/or retraction of herbaceous plain and forest vegetation. Variations in vegetation composition over the last 7168–7260 cal yr BP in the Formoso River estuary reflects the strong influence of sea-level variations, which were responsible for changes in coastal paleogeography and paleogeomorphology. Changes in vegetation composition indicate its close relationship with transgressive and regressive marine events and corresponding variation of the depositional environment like lakes to coastal lagoons, tidal channels, sandy strand-plain, and the modern estuary of the Formoso River.