THE GRAVELS OF THE RIO DE LA PLATA: THE HOLOCENE BEACHES OF BELLA VISTA, URUGUAY

ISLA F.I.; ESPINOSA, M.A.

JOURNAL OF COASTAL RESEARCH

COASTAL EDUCATION & RESEARCH FOUNDATION

Año: 2021 vol. 37 p. 987 - 992

0749-0208

The Río de la Plata has a ría-type estuary, with a coastal plain dominated by fine to very fine sands to the south, and a tectonic coast to the north, dominated by fine to coarse sand. Although the headlands of the river were dominated by fluvial processes related to the deltaic lobes of the Parana River, the Paraná Guazú and Paraná de las Palmas, the outer estuary is subject to wave action that increased significantly during storms from the SE. Wave statistics confirmed a littoral drift responsible for the spits at the outlets of affluent rivers deflected to the west (Solís Grande, Solís Chico). At the northern Uruguayan coast the interval between Bella Vista and Las Flores are composed of gravel whose description is here first reported. Bella Vista beach has two berms, the upper berm is partially covered by eolian sands. On the other hand, Las Flores beach consists on a single berm where gravels segregate upwards and sand towards the river coastline. The storm berm of Bella Vista contents finer gravels (3-6 cm) while the gravels from the tidal berms (both beaches) are coarser, from 6 to 15 cm. According to the Zingg diagram, oblate and tabular gravels abraded by the wave action dominate. Considering old photographs these gravel berms are stable and relict from the highstand of the Middle Holocene. They were therefore derived by waves from submerged deposits originally derived from the Complex Sierra de las Animas