Análisis paleoambiental en una secuencia del Holoceno tardío de Arroyo Claromecó (Buenos Aires) basado en diatomeas.

HASSAN, G., ESPINOSA, M. A. & ISLA, F.I.

AMEGHINIANA

APA

Lugar: Buenos Aires; Año: 2004 vol. 40 p. 161 - 170

0002-7014

The diatom assemblages of a sequence outcropping at the left margin of the Claromecó were studied in order to characterize paleoenvironments in terms of salinity and depth. The analyzed profile comprises an interval between 2430 ± 80 and 840 ± 70 14C years BP. The results of diatom counts were analyzed considering the ecological characteristics of each taxon. Epiphytic and oligohalobous indifferent taxa are present in significant proportions along the whole sequence, dominating Cocconeis placentula (epiphytic and oligohalobous indifferent), Cyclotella meneghiniana (planktonic and oligohalobous halophilous) and Navicula capitata var. hungarica (benthic and oligohalobous indifferent). At the base, Synedra acus (planktonic and oligohalobous indifferent) and Nitzschia amphibia (epiphytic and oligohalobous indifferent) were also founded. At the middle of the section, the frecuence of tychoplankton and oligohalobous indifferent taxa (Fragilaria construens and F. virescens) increased. About 840 14C years BP higher proportions of brackish taxa become present: Pleurosira laevis (epiphytic and mesohalobous), Surirella striatula and Hyalodiscus subtilis (benthic and mesohalobous). The presence of brackish to freshwater diatoms and higher proportions of epiphytes, associated to tychoplanktonic, planktonic and benthic specimens led to infer a shallow-water environment with vegetation and subject to water level and salinity variations. These variations were probably caused by changes in precipitation/evaporation balance.