Reconstrucción Paleoambiental de la Planicie Costera de Mar Chiquita (Provincia de Buenos Aires, Argentina) Durante el Holoceno, Basada en Diatomeas

Abstract. HOLOCENE PALEOENVIRONMENTAL RECONSTRUCTION OF THE MAR CHIQUITA COASTAL PLAIN (BUENOS AIRES PROVINCE, ARGENTINA) BASED ON DIATOMS. Diatom assemblages from a core at the north of Mar Chiquita coastal plain were analyzed in order to identify environmental changes due to salinity and depth. The core contains sediments dated at the base in 5802±70 14C years BP. Four lithological units were defined: greenish-grey silt, brownish-grey sandy silt, heterolithic facies and brown sandy silt. Two hundred diatom species were identified and grouped based on their salinity tolerances and life form. Cluster analysis defined two diatom zones. The lower section of the sedimentary sequence (from the base to 90 cm depth, Zone I) was dominated by Paralia sulcata (Ehrenberg) Cleve and Psammococconeis cf. disculoides (Hustedt) Garcia accompanied by marine-brackish plankton, epipsammon and epiphytes indicating coastal marine conditions. From 90 cm towards the top (Zone II), salinity and depth decrease: P. sulcata declin...