Reviewing sedimentological and hydrodynamic data of large shallow coastal lagoons for defining mud depocenters as environmental monitoring sites

• Published in: Sedimentary geology Vol. 410; p. 105782
• Main Authors: Bortolin, E.C., Weschenfelder, J., Fernandes, E.H., Bitencourt, L.P., Möller, O.O., García-Rodríguez, F., Toldo, E.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2020
• Subjects: Back-Barrier Lagoon; Hydrodynamics; Morphometry; Mud depocenter; Sedimentology; Sedimentology; Hydrodynamics; Back-Barrier Lagoon; Morphometry; Mud depocenter
• ISSN: 0037-0738; 1879-0968
• DOI: 10.1016/j.sedgeo.2020.105782

We reviewed historical data on surface sediment composition/distribution and hydrodynamics of the Patos-Mirim lagoonal system, the largest coastal shallow limnological system of the world, located in eastern South America, which is ca.15,000 km2, the maximum length is almost 500 km and maximum depth is around 7 m. We inferred the geographical position of six mud depocenters in relation to the hydrodynamic conditions evolved from predominant winds and morphometry. Littoral zones of sediment resuspension dominated by sand were identified where current velocity was higher than 0.2 m s−1 and depth was <5 m. In addition, central zones were susceptible to deposition of fine sediment fractions, where current velocity was close to 0.1 m s−1 and depth was >5 m. Such conditions observed for the central zones represent appropriate morphodynamic controls for mud depocenter formation. The six permanent Holocene depocenters for the whole Patos-Mirim system were all dominated mostly by silty clayey facies and exhibited an Mz value equal to or higher than 7.5. Because of the dominance of the fine fraction, we propose them as future potential key-spots for monitoring the environmental quality of the system to assist regional sustainable management.