Paleoenvironments and clogging of the River Plate anthropogenic lagoon Ecological Reserve Ciudad Universitaria- Costanera Norte (Buenos Aires, Argentina)

Sedimentation in the estuarine plain of the River Plate modifies the landscape of the nature reserves of the Ciudad Aut??noma de Buenos Aires. These reserves were generated by the artificial construc-tion of embankments that polderized sectors of the coast and gave rise to wetland ecosystems. This contribution aims to study the paleoenviron-ments and vertical accretion rates of the Reserva Ecol??gica Ciudad Universitaria -Costanera Norte, a small anthropogenic lagoon built in the 1970s. For this purpose, two cores were extracted: one at the mouth of the lagoon and the other in its interior. Granulometry, moisture, organic matter, micropaleobiological and artifact contents were analyzed in each core. The obtained record was divided into two stratigraphic units. At the base, a massive sand unit that belongs to the estuarine plain that precedes the artificial polderization, and, in the upper part, a muddy unit with the presence of plastic and lithic artifacts, accumu-lated after polderization. The sedimentation rate obtained at the mouth of the lagoon was 1.2 cm of vertical accretion per year, while in the interior the accumulation was 0.7 cm per year. The micropaleobiological analysis allowed us to interpret that the sedimentation in the interior of the lagoon was gradual and with a trend towards eutrophication of the water column. Management of these protected coastal wetland ecosystems must consider the rapid sedimentation of the lagoon and the replacement of frequently flooded low marsh environments with rarely flooded high marshes dominated by rooted wetland plants.