Paleoenvironmental reconstruction of the Maricá Lagoon, RJ, based on benthic foraminifera

Abstract

In order to evaluate the coastal evolution based on the distribution of benthic foraminifera associated with sedimentological features, two cores were drilled at the Maricá Lagoon, Rio de Janeiro. Two biofacies were recognized: (i) Ap-At (Ammonia parkinsoniana - A. tepida) biofacies - corresponding to the lower portion of the cores, characterized by abundance of calcareous-hyaline foraminifera, such as Ammonia parkinsoniana and A. tepida, associated with the intercalation of silty mud and sandy mud with abrasion and broken shells, suggesting storm wave events; and (ii) Ac-As (Ammotium cassis - A. salsum) biofacies – comprising the upper portion of the cores, characterized by agglutinated species, such as Ammotium cassis, A. salsum, Trochammina inflata, Miliammina fusca, Ammobaculites spp., associated with silty mud and occurrence of microshells, indicating a low energy environment. This record of calcareous and hyaline foraminifera distribution is mainly related with the dynamic opening and closing of the sandy barriers Maricá Lagoon.