CONICET | Buscador de Institutos y Recursos Humanos

The Parana Delta of the Rio de la Plata estuary boarders some of the most populated areas of South America and builds from one of the ten largest rivers in the world, yet still is yielding new insights. While the lower part of the delta has received much attention, the upper part is only recently studied. Integration of this segment permits a more holistic story of delta evolution and reveals some unique aspects of evolution for the Atlantic coast. The complex history of the delta starts at sea-level highstand before 8,000 yr BP and lasting to 6,500 yr BP, continues through a falling stage at 6,500 yr BP to 4,500 yr BP, and levels into a lowstand from 4,500 yr BP to Present. The initial highstand delta was fluvial dominate, but altered to a mixed wave-dominate delta by ~8,000 yr BP. The fluvial highstand delta predates the oldest beach cheniers of 8,100 yr BP, and postdates the underlying transgressive muds at 9,300 yr BP. After a period of wave-delta propagation, relative sea-level began to fall and forced downstepping of the shoreface producing a falling stage systems tract. During this time, the waves refracted around intraesturay islands which altered the trajectory of chennier building. Shortly after downstep ceased, at about 4,500 yr BP, the delta returned to a fluvial dominated delta system, which remains the case until today. The current delta has aggraded with sea-level rise since ~1,000 yr BP. Early rise and stabilization of relative sea level that initiated the highstand was accomplished by localized tectonic uplift in the Rio de la Plata Estuary resulting in the anomalously early initiation of the highstand delta. At well over 8,000 yr BP the South American shoreline here hit relative sea-level maximum relatively early, and makes the Parana a candidate for the oldest regressive Holocene delta in the world. At

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