Spit-Inlet migration and storm-driven stacking at Praia de Leste Holocene barrier, southern Brazil

Abstract

The interaction between coastal drift-dependent features, such as spit and inlet systems and the dynamics of estuaries, under the effect of tides, produces significant changes in coastal barriers depositional architecture. Extreme events associated with these autogenic factors insert elements of variability into the depositional architecture of these deposits. OSL (Optically Stimulated Luminescence) dating in the Holocene barrier of Praia de Leste, in the southern region of Brazil, associated with GPR (Ground Penetrating Radar) subsurface surveys and stratigraphic profiles at outcrops, identified a pattern of retrogradational stacking and truncation in the beach ridges, formed by local patterns of erosion and deposition, between the last relative maximum sea level and the beginning of progradation of the Holocene barrier. The predominance of a longshore drift in an opposite direction to the current one between 5.1 ± 0.3 ka and 4.1 ± 0.3 ka is suggested by the migration of spits and the displacement of a paleo-inlet to the southwest, later abandoned during the slow and gradual fall of the relative sea level (RSL) and consequent diminution of the estuary tidal prism.