Marine oscillatory movements during the Late Holocene in the lower course of the Piranhas-Açu River, Rio Grande do Norte – Brazil

In Brazil, discussions about oscillation events of the mean sea level after the Holocene climatic optimum period, which corresponds to the end of the MIS1 transgressive maximum (RAILSBACK, 2015), demonstrate predominantly divergent conclusions. This may be motivated by the complexity in understanding coastal landscapes along an extensive coastline with distinct evolutionary dynamics. One of the geomorphological evidences produced as a result of eustatic processes are marine terraces, which behave as good geoindicators. These are characterized as sandy deposits, represented by old lines of beaches, formed after a sea level rise, in regressive episodes. The objective of this work is to analyze marine terraces, formed during the Meghalayan (Upper Holocene – 4.250 years BP) located in the lower course of the Piranhas-Açu River, Rio Grande do Norte – Brazil. Through dating obtained by Optically Stimulated Luminescence - OSL, applied to their surficial covers. We chose to perform OSL dating only on the surficial parts of the deposits, as they can provide information over the last period in which the sea was present, depositing sediments at that location. The identification of 4 marine terraces levels demonstrates the occurrence of 4 depositional and regressive moments of the sea, identified in the surficial covers present in level I, aged 3.475 ± 210 years BP, level II, aged between 2.585 ± 165 years BP and 2.245 ± 260 years BP, level III, aged 1.710 ± 110 years BP, and level IV, aged 365 ± 40 years BP and 290 ± 50 years BP. We also verified in this research that short-term climatic events behaved as the main drivers of changes related to marine transgressions and regressions, consequently influencing the genesis of the contextualized terraces.