ON THE RELATIONSHIP BETWEEN HOLOCENE ENVIRONMENTAL VARIABILITY AND DIATOM COMPOSITION IN THE PEÑA LAGOON, SE URUGUAY

LAURA DEL PUERTO; CAROLINA CUÑA; HUGO INDA; EDUARDO L PIOVANO; FELIPE GARCÍA-RODRÍGUEZ

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2018

0002-7014

Abstract. Uruguayan Southern lagoons exhibit high Holocene resolution paleoenvironmental-paleoclimatic records for inferring long-term regionalchanges. The multiproxy analysis of three sediment cores enabled the recognition of Holocene climatic variability from the paleolimnologicalrecord of the Peña lagoon over the last 2,458 cal. years BP. Four main stages were identified throughout the record. The first stage(2,458?1,500 cal. years BP) was characterized as a shallow meso-eutrophic system with high abundances of aerophilic benthic species, epiphytictaxa and planktonic taxa. The second stage (1,415?390 cal. years BP) showed a noticeable change in the diatom assemblage dominatedby the fresh-brackish benthic species Staurosira construens, but also presented fluctuations in the abundance of Aulacoseira ambigua and Aulacoseiragranulata, which indicate the occurrence of temperate to cold and semiarid climatic conditions including intervals of high rainfall. The corechronology allowed us to ascribe this stage to the Little Ice Age (LIA). The third stage, post 390 cal. years BP, showed the highest proportionof freshwater planktonic species throughout the entire core, thus indicating the development of an eutrophic system under relatively warm andwet conditions, which were assigned to the Current Warm Period. After ca. 1,962 AD, a sharp increase in the abundance of epiphytic specieshighlights the onset of the fourth stage, which was characterized by littoral expansion and, consequently, the proliferation of associated macrophytesdue to anthropogenic impacts.