Late Quaternary infilling of the Assu River embayment and related sea level changes in NE Brazil

A detailed geomorphological survey using Light Detection and Ranging (LiDAR) was carried out along the western part of the Assu River valley, NE, Brazil. The study was complemented by the investigation of sedimentological, mineralogical, and sediment benthic foraminifera indicators within the 14C geochronological framework. The integration of data sets permitted the reconstruction of the main phases in the evolution of this area during the Holocene. The shallow embayment, which is now completely infilled, acquired its present form within the limits of antecedent morphology developed since the last interglacial period. The main forcing factors responsible for repositioning the shoreline, which ran along the strike-slip Afonso Bezerra fault at an angle of approximately 35° to the present coast in the Early/Mid Holocene, were as follows: (1) tectonic activity along the strike-slip Afonso Bezerra fault, (2) fast inundation of the shallow paleo-valley embayment during the last pulse of Holocene transgression ca. 8000 cal yr BP, (3) advance of the Assu river mouth through accretion of fluvial bay head delta and costal drift sediments and (4) sheltering of embayment by barrier islands which permitted a widespread development of mangrove forest during the last 3 millennia. The estimated rate of progradation of the Assu estuary that led to the present stage of terminal infilling is in the order of 3-4 m/yr.