ESPINOSA Marcela Alcira
congresos y reuniones científicas
Paleoecología de diatomeas del delta de la albufera Mar Chiquita, Buenos Aires
ESPINOSA, MARCELA A.
Congreso; II Reunión Argentina de Limnología; 1991
Instituto de Limnología Dr. Raúl Ringuelet (UNLP-CONICET).
A 68 cm thick outcrop of diatomaceous sediments at the head of Mar Chiquita Lagoon on the Argentine coast near Buenos Aires provides evidence of Holocene paleoenvironmental changes related toa the sea level changes and freshwater input to the lagoon system. Salinity tolerances of extant diatom taxa were used for the reconstruction and multivariate analytical techniques were applied to reduce subjetive interpretations of the diatom percentage data. The basal half of the record was deposited before 3000 years ago and fossil diatoms indicate generally freshwater conditions with one fluctuation in mesohalobous diatoms suggesting brackish water conditions at a depth of about 60 cm. Polyhalobous (marine) diatoms characterize the record after 3000 years ago and large numbers of epiphytic diatoms indicate salt marsh environments with episodic sea water fluctuations to supratidal levels. Freshwater diatoms returned at the top of the outcrop, presumably as a result of the restriction of the historic marine inlet to the lagoon and the effects of freshwater inflow to the basin.