Late Holocene coastal dynamics and relative sea-level changes in the littoral of Paraíba,northeastern Brazil

Abstract

A preliminary analysis of a segment of the Paraíba littoral in northeastern Brazil revealed a prograding shoreline in a coast currently characterized by estuarine transgressive depositional systems. Detailed study of coastal geomorphology is of relevance to reconstruct the sea-level history in this shoreline. Such investigation can help improve the record of past sea-level curves of northeastern Brazil, an issue still open to debates. In this work, we explored remote sensing imagery for the geomorphological characterization of this prograding shoreline and combined this information with geological field data aiming to establish the various phases of shoreline progradation. In addition, we also analyzed the potential forcing factors responsible for the morphological changes in the eastern section of the littoral of Paraíba during the late Holocene, comparing changes with other prograding shorelines along the east coast of Brazil. Geomorphological interpretation was based on the analysis of Phased Array type L-band Synthetic Aperture Radar (PALSAR) images acquired aboard the Advanced Land Observing Satellite 1 (ALOS-1). Geological data comprised dating of sand samples by the optically stimulated luminescence (OSL) technique for the establishment of the chronological context. The coastal deposits are represented by a cuspate morphology and numerous internal beach ridges that prograded seaward from a roughly north–south trending palaeocliff. The chronological data indicate shoreline progradation during the past 2.1 ± 0.1 ka, after the mid-Holocene sea-level fall. Several prograding episodes occurred during this time, some not matching with proposed sea-level rises punctuated upon the overall fall. Together with the regional geological context of the study area, we propose that eustatic sea-level was not the only factor triggering coastal progradation in this region.